Don't look a gift horse in the mouth. That's what they say at least. 

When it comes to Fantasy Baseball nothing could be further from the truth. Fantasy owners have been given gifts in the first month of the season in the form of surprising pitching performances and you should absolutely look closer before you buy in. 

Here are five that look primed to regress and what you should do about it.

Dylan Bundy
NYM • SP
2017 Stats
ERA2.17
WHIP1.05
WINS5
K/95.5
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It's not just that Dylan Bundy has been lucky. He's been pretty bad. Of pitchers that have thrown at least 40 innings this season, only Alex Cobb has a lower strikeout rate. No pitcher with as many innings as Bundy has a ground ball rate as low as his 31 percent. Pitchers that don't strike anyone out and don't get ground balls are almost universally bad pitchers. Few have done it over the past five years and been able to accumulate enough innings to qualify.

Digging deeper, things don't look any better. Bundy's fastball velocity is down two miles per hour and his swinging strike rate is at 9.8 percent. That's not too far removed from his career average of 10.3 percent, but we were hoping Bundy was going to take a step forward in 2017. Despite the sparkling results, he has not done that yet.

I say yet because I don't really believe that Bundy has lost the ability to strike hitters out. He was an elite strikeout pitcher for most of his time in the minor leagues and he was above average last year. He's not that far off league average in swinging strike rate (10.3 percent) and his improved control makes a small drop off in Ks acceptable. 

I still rank Bundy as a low-end No. 3 starter in Rotisserie leagues, where his value isn't skewed by SPARP eligibility. In other words, you shouldn't give him away. At the same time, if you can find someone to buy in to his ERA and offer you a solid No. 2 starter I would make the deal in a heartbeat.  

Dallas Keuchel
MIN • SP • #60
2017 stats
ERA1.88
WHIP.85
WINS5
K/97.01
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Dallas Keuchel has done this before. That's what I'm being told at least. 

He did win a Cy Young in 2015, but that can't be what people are talking about. In that year he struck out 8.4 batters per nine innings and had a career best 4.2 K/BB ratio. This year he's barely fanning more than 7 batters per nine innings and has a good, but not great, 3.15 K/BB ratio (30th in MLB). 

Maybe they meant 2014 when Keuchel made me look silly by breaking out with a 2.93 ERA despite only striking out 6.6 batters per nine. He also had a similar ground ball rate (63 percent) and BB/9 (2.2). Of course, he also gave up a .295 BABIP and had a 79.4 percent strand rate that season. This year he's at .195 allowed with a 93 percent strand rate. 

That explains why Keuchel's FIP (3.72) isn't in the same neighborhood as his ERA and why he's my favorite sell high candidate. I'm not saying Keuchel is bad; he's quite good. I just don't value him like a Fantasy ace, and many do. I'd gladly deal him for Jacob deGrom, Stephen Strasburg or Carlos Carrasco, and enjoy the fact that I just benefited from the best month of Keuchel's season. 

Lance Lynn
STL • SP • #31
2017 Stats
ERA2.04
WHIP1.08
BABIP.234
STRAND RATE87.9%
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Lance Lynn was one of my favorite sleeper picks coming into this year, so I'm torn. On one hand I'm very happy to have benefitted from a successful first six starts. I'm also sad to tell you that you shouldn't get too excited by it. Lynn's ERA is basically half of his FIP as he's pitched like a league average pitcher.

This is really nothing new for Lynn, who has often had the peripherals of a league-average pitcher only to deliver better results for his Fantasy owners. I'm still thrilled to have landed him as a No. 4 or No. 5 starter, but I wouldn't hesitate to deal him if someone thinks he's worth more than that. 

Seung-Hwan Oh
COL • RP • #18
2017 Stats
ERA3.45
FIP5.17
K/97.47
BB/92.87
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The popular assumption is that Seung-Hwan Oh struggled to begin the year but has largely figured things out and is fine. After all, he hasn't given up an earned run or blown a save since April 17. Fine, let's forget about those first five games and just look at his last nine appearances. 

Oh has struck out 11 batters in 10 innings, which is good. He has also allowed 12 base runners and three unearned runs (courtesy of one three-run home run). That's a 25 percent K rate, a 9 percent BB rate and a 3.30 FIP. Compare that to his 33 percent K rate, 6 percent BB rate and 2.13 FIP from 2016 and you can plainly see he's still not been the pitcher he was.

Closer has been a volatile position early this year so there's no chance I'd be looking to replace Oh, but I also think it's fair to still have concerns. I value him as a solid No. 2 closer, which is below my expectations for him heading into the year.

Derek Holland
BOS • SP • #22
2017 stats
ERA2.02
K/97.57
BABIP.220
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You guys know this Derek Holland thing isn't real, right? I thought so, but I've heard enough chatter to dispel it. Holland hasn't been good since 2013 and he isn't good now. He has a 3.67 FIP, a 4.77 xFIP and a 4.35 SIERA. He's pitching for one of the worst teams in baseball, one that has an average-at-best defense. He's given up seven unearned runs already. Don't pick up Derek Holland, this won't end well.