10 Fantasy Baseball Players to Buy and Sell for Week 13

Jimmy Nelson has completely transformed his game this season, yet might still be able to be had for cheap due to his career pedigree.

As we enter week 13, we're nearing the midpoint of the MLB season. By now, most owners are reaching decisions regarding their teams.

Maybe your team has been plagued by injuries and it is time to cut bait on guys you would have preferred to hold on to because you're in win-now mode. Maybe you have a comfortable lead in the standings and can afford to take a chance on some buy-low players in hopes of a bounce back heading into the later stages of the season.

Regardless of where your team sits right now, you should always be looking to take advantage of market inefficiencies on players.

Perhaps a slow start is just a product of bad luck and a small sample size. Maybe the reason you're in first place is due to the stellar but possibly unsustainable play of some players you can sell high on. If you're not sure whether you should hold or fold on a player, don't sweat it. That's why we're here.

The following 10 players have seen a perceived change in their fantasy stock, and we'll attempt to decipher which warrant taking action.

Hold Miguel Cabrera

Miguel Cabrera has been a huge disappointment this season -- he's on pace for a career-worst .261 batting average, .430 slugging percentage, and 20.6% strikeout rate, all while battling through oblique and groin injuries. While his fantasy returns certainly haven't been what owners expected when they invested an early-round pick on him, there is reason to believe he could have a big second half in store.

For starters, no player has a larger discrepancy between their wOBA and xwOBA, or expected wOBA. Cabrera's .337 wOBA is a career low, but his xwOBA of .414 ranks eighth among qualified hitters and fourth among first baseman. Another encouraging sign for Cabrera is his career-high 47.2% hard-hit rate, which is the sixth-highest in the league.

The bottom line is, all you're going to get for Cabrera at this point are low-ball offers. Considering most of his peripherals line up with the elite hitter we have seen in years past, the best thing to do is hope for some statistical correction and a healthier Miggy in the second half, with some much-needed rest right around the corner in the form of All-Star Break.

Buy Jimmy Nelson

After back-to-back seasons of posting an ERA and xFIP above 4.00, Jimmy Nelson has posted an identical 3.50 ERA and xFIP this season. What's even more surprising is the fact that he has done so despite a career-worst .341 BABIP -- the sixth-highest mark in the league. Nelson is one of 17 pitchers with a BABIP above .320, and he is the only one with an ERA below 4.00.

He's been even more effective as of late, as his 2.54 xFIP over the past 30 days is the third highest among qualified starting pitchers.

Perhaps the most surprising aspect of Nelson's game has been his increase in strikeouts. A career 7.63 strikeout-per-nine-innings (K/9) guy, Nelson has struck out 9.3 batters per nine in 2017. He's struck out at least eight batters in six of his past nine starts, a span during which he has a 10.49 K/9.

Due to a career pedigree of mediocrity, Nelson might still be able to be had fairly cheap in trades, as many owners could be skeptical to buy in. His bad luck on balls in play and early-season struggles also are helping his case as a buy-low guy, as his season-long numbers don't jump off the page.

Sell Ariel Miranda

The window to sell high on Ariel Miranda might be closing, as he has allowed a combined 12 runs over his past three starts, but the discrepancy between his peripherals and base numbers is still large enough that it is worth seeing what you could get for him on the trade market.

Miranda's season 4.11 ERA is a far cry from his putrid 5.38 xFIP. While that may seem bad, he has been unbelievably bad over the past month. Over the last 30 days, no pitcher has a worse xFIP than Miranda's 6.34 mark. Even so, he has maintained a respectable 3.96 ERA during that span thanks to an unsustainably low BABIP of .179.

Miranda's already unimpressive 6.85 K/9 is down to a far-from-useful 4.42 mark over his past 30 days, which barely tops his 3.26 BB/9 mark during that span. He also has allowed the highest fly-ball rate (55.1%) during that span, which is a troubling sign going forward.

He's been a usable pitcher this season, but his underlying numbers point towards someone who belongs on the waiver wire in most leagues. If you can get a decent offer for him based on his base numbers, jump on it while you still can.

Hold Carlos Santana

Right up there with Miggy in terms of discrepancy between xwOBA and wOBA is the perennial slow-starter, Carlos Santana. Santana has posted just a .306 wOBA this season, down from an xwOBA of .354, which gives him the fifth-largest negative discrepancy.

While his early-season struggles have been frustrating, Santana's first- and second-half splits suggest his slow start really isn't that far out of the norm. He has just a career .341 wOBA and .420 slugging percentage in the first half, as opposed to a .363 wOBA and .464 slugging percentage in the second half.

Santana's early-season slump has been slightly worse this year, so his overall numbers might not end up being what you drafted him for, but if history is any indicator, he should turn it on soon. Similar to Cabrera, you're not going to get a fair offer for him at this point, so the best course of action is to wait it out.

Buy Masahiro Tanaka

Masahiro Tanaka has been one of the most frustrating pitchers to own this season, posting a 5.74 ERA, in spite of a 3.90 xFIP. He's also been maddeningly inconsistent, mixing good starts with bad ones -- over his past six starts, he has allowed at least five runs as many times as he has allowed one or fewer runs.

He's also posted his strongest strikeout numbers (9.04 K/9) since his rookie campaign (9.31 K/9), during which he posted a 2.77 ERA.

In the month of June, only six starting pitchers have posted a lower xFIP than Tanaka's 3.04 mark, while only seven have a stronger K/9 than his 11.03 mark.

More than likely, Tanaka owners are going to be frustrated with his inconsistency for the past three months. If you can get him for cheap, his peripherals suggest there's a good chance he could turn his disaster of a season around and be a high-upside pitcher.

Sell Trey Mancini

The Trey Mancini breakout has been an exciting one -- over the past two weeks, the young slugger has posted a .426 batting average and .815 slugging percentage. While it has been fun to ride the hot streak, a look at his underlying numbers suggest it would be worthwhile to seek out trade offers on him while his value is at its peak.

During that span, no player has a higher BABIP than Mancini's bloated .545 mark. He's also inside the top 15 in home-run-to-fly-ball-rate, as he has launched five homers over the past two weeks despite a 60.5% ground-ball rate.

That ground-ball rate is probably the most troubling aspect of Mancini's hitter profile. His career 69.0% contact rate and 26.4% strikeout rate are more in line with a swing-and-miss power hitter, but his career 48.4% ground-ball rate could certainly put a cap on his power potential. His low contact rate also suggests he is not anywhere near the career .323 hitter he has been. Once his .382 career BABIP drops, it is likely that he caps out as more of a mid .200s hitter.

Buy Brandon Belt

Brandon Belt, holder of a career .334 BABIP and .268 batting average, has seen those numbers drop to a .264 and .228 this season, respectively. His struggles in the batting average department might be enough to mask the fact that he has made solid strides forward in the power department.

Belt is on pace to crush 29 long balls, which would be a huge improvement from his previous career-high 18. His improved power stroke can be traced back to his 42.0% fly-ball rate and 36.7% hard-hit rate, both of which are improvements over his career numbers.

Belt is yet another hitter who appears to be in line for some positive regression in wOBA, as the difference between his wOBA (.338) and xwOBA (.382) is the ninth-largest in the league. When he begins to see some better luck on balls put in play, his average should fall more in line with his career .268 batting average. If that does come to fruition and he is able to maintain his power, he could be a dangerous hitter over the final few months of the season.

Hold Kyle Schwarber

Kyle Schwarber has been perhaps the most disappointing hitter this season, as he posted just a .171 batting average through 64 games before being sent down to Triple-A. Considering his impressive rookie campaign and playoff contributions last season, fantasy owners were expecting much more from the youngster in 2017.

As a result of his demotion, Schwarber has been one of the most-frequently dropped fantasy players across all formats, but a look at his underlying numbers suggests there is still hope worth holding onto if you're an owner of the talented outfielder.

For starters, his 75.3% contact rate is on pace to be a career best, while he's cut down on his swinging-strike rate (10.8%). His hard-hit rate (32.0%) is a bit down from his career mark, but is still above the league average mark. The main issue has been that his BABIP is down to just .193 mark, which makes him the only qualified hitter in the league with a mark below .200 entering action on Monday.

Schwarber has the talent to be a difference maker in leagues, so unless you absolutely cannot afford to wait for him to figure things out, the best course of action would be to hold onto him.

Sell Matt Davidson

Matt Davidson has become a hot commodity, as the hard-hitting 26-year old has launched seven dingers over the past two weeks, putting his season-long total up to 17. He's also posted a respectable .260 batting average despite averages of .268, .203, and .199 in his past three seasons at Triple-A. If not for a .349 BABIP, Davidson's 65.9% contact rate and 38.7% strikeout rate would likely add up to a low .200's hitter.

Over the past 30 days, Davidson's free-swinging ways have been on full display, as he is the owner of the league's sixth-lowest contact rate (64%) and the fourth-highest swinging-strike rate (18.3%) while swinging at an alarming 39.7% of pitches outside the zone.

The power may be legit for Davidson, but the clear holes in his swing are going to cause cold streaks. His inflated BABIP has kept him from being exposed too much, so this would appear to be the optimal time to sell on him, before he does endure an inevitable cold streak.

Buy Jeff Samardzija

Jeff Samardzija bounced back from a shelling at Coors Field to post seven strong innings against the Atlanta Braves in his last start and now has his ERA down to a usable, but not noteworthy 4.74 ERA. So, what about the Shark makes him stand out as an incredible buy-low option?

A look at his peripherals suggests that despite his base numbers, he has been one of the league's most dominant pitchers. He ranks behind just Chris Sale, Lance McCullers, and Clayton Kershaw in xFIP this season, with a 3.01 mark that is nearly two runs below his ERA.

His elite xFIP is primarily fueled by some incredible ratios in the strikeout-to-walk ratio. On the year, Samardzija's 10.22 K/9 would be a career best, while his BB/9 is down to 1.19, which would also be a new personal best. He's been even more efficient over the past month, as he has posted a league-best strikeout-to-walk ratio of 16.5, which is nearly double the next-highest mark.

Samardzija has been a frustrating pitcher to own this season thanks to bad luck on balls in play (.327 BABIP) and pitching for an inept San Francisco Giants squad. If his owner is ready to cut bait on the talented right-hander, be the first in line with buy-low offers.