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The Rays have been forced to go with some unorthodox rotation choices this season, as no club in the majors has been hit by injuries as hard so far. They've had eight different pitchers start a game this season, ranging from the obvious -- Jake Odorizzi and Chris Archer are rotation mainstays -- to the off-the-wall, as when middle reliever Steve Geltz started his first game as a professional.

The results have been better than they have any right to be; the Rays have the fifth-best rotation ERA in baseball. One of the key contributors has been 27-year-old Nathan Karns, who won his third decision in a row last Wednesday, and has a 2.95 ERA in seven starts since opening up the season with a dud.

Karns has been added in 28 percent of CBSSports.com leagues over the last week, and enters Week 7 as a two-start pitcher. However, he is still available in 35 percent of leagues; should owners be more aggressive about scooping him up?

Karns has been on quite a roll over his last seven starts, with 40 strikeouts in 39 2/3 innings to go along with his pretty ERA. He currently rates out as a better Fantasy option than some pretty big names, like Jon Lester, David Price and Clayton Kershaw. He gets to face off against the Braves to open his two-start week, and that should be enough to keep him active in Week 7, given the roll he is on. However, should Fantasy players expect this to be sustainable?

I'm not so sure about that. Karns should have his uses in the short term, but there are warning signs. The strikeout rate is nice, but the rest of Karns game leaves a bit to be desired. 49.6 percent of Karns' batted balls have been hit on the ground, a pretty good sign, but also not at all in line with what he produced in the minors, when he had a 44.1 percent groundball rate. That's a solid number, but not exactly elite, especially since Karns' HR/FB rate is 13.3, a bit high.

More concerning, is the fact Karns' control has been an issue. He is walking 4.2 batters per nine, leaving him with a K:BB ratio just above two, hardly great. Add it all up, and you are left with a 4.45 FIP and 4.12 xFIP, neither of which suggests good things in Karns' future.

The Rays do have a good defense and play in a good park, so Karns outperforming his defense independent stats wouldn't be a surprise. Still, it might be asking a lot for him to remain much more than just a streaming option. He should be well worth using in Week 7 with two starts, but could be droppable beyond.

Lance McCullers, Astros (39 percent owned)

McCullers is the most-added player in CBSSports.com leagues over the last week, despite not having made his major-league debut. That will come Monday night, when he takes on the A's, and it will come without McCullers having thrown a pitch above Double-A. In fact, the 21-year-old has faced just 16 batters above Class-A, which raises the question of how ready he is for the majors. Pitchers have made the jump from the low minors to the majors with success before, but you have to be really special to do it, obviously. Jose Fernandez made the jump from High-A to the majors, but that was coming off a 1.75 ERA between two Class A levels. McCullers spent all of 2014 at High-A Lancaster, where he posted an ugly 5.47 ERA, albeit in one of the most hitter-friendly leagues in professional baseball. McCullers has the raw stuff to succeed in the majors someday, with a fastball-curve combination that project to be plus offerings. However, he has walked 4.6 batters per nine innings throughout his minor-league career and has been plagued by command issues consistently. His upside is high, but McCullers might also wind up as a reliever in the long run. He should get two starts in Week 7, and might be worth throwing out there in deeper leagues for his strikeout potential alone. However, he is a high-risk option, so you shouldn't be dropping anyone you are counting on for him.

Mike Bolsinger, Dodgers (11 percent owned)

Much like the Rays, the Dodgers have been forced to pick from the scrap heap for their rotation. Bolsinger has been the best of the bunch so far, posting a 1.04 ERA in three starts, after failing to crack the Diamondbacks rotation in the spring. The Dodgers apparently saw something in Bolsinger's 3.41 minor-league ERA, and he has racked up a bunch of groundballs en route to his solid start. He is striking out just 7.3 per nine innings, but his previous major and minor-league track record suggest he might be able to add a tick or two in that category before long. Bolsinger isn't a future ERA champ, but he did have a 3.31 xFIP in 52 1/3 innings with the Diamondbacks last season, so there is room for some optimism. He is probably just an NL-only option at this point, but he looks like he could emerge as a consistent start with that team behind him.

Brad Miller, Mariners (31 percent owned)

There was a lot of excitement around Miller a few years back, after he posted a massive .319/.399/.521 in the minors in 2013 as a middle infielder. His first exposure to the majors was a mixed bag; he held his own in 2013 over 76 games, but slumped to a .221/.288/.365 line in 2014. After a four-homers-in-five-games run over the last week, Miller is starting to look like the player we were all hoping for, with a .264/.328/.500 line for the season under his belt. Much of that is inflated by his recent run, sure, but there are reasons to be hopeful overall. Miller has cut his strikeout rate from 23.1 percent to 20.2 this season, and his rate of hard-hit balls and line drives is up a few percentage points as well. However, just one-fifth of his batted-balls so far have been hit in the air, making it hard for him to sustain a breakout power season unless that changes. Still, given his pedigree and minor-league track record, Miller's talent level is still worth betting on, especially with how hard it is to find production at shortstop and middle infield. He is worth a look even in mixed leagues.

Josh Harrison, Pirates (84 percent owned)

Harrison was one of 2014's big breakout stars, but there was a lot of deserved doubt about whether he could sustain that level of production. Through the first month and a half of his follow-up season, Harrison has failed pretty spectacularly, and his ownership dropped predictably as a result. Any player with a limited track record is going to be on the chopping block if he can't shake the "fluke" label quickly. For as much as I doubted Harrison after last season's BABIP-fueled breakout, I think he's considerably better than he has shown this season, and we're starting to get a feel for that in May. He is hitting .255/.293/.418 in May, despite a .250 BABIP. Harrison is a solid contract hitter who got a bit strikeout-happy early in the season. But he has whiffed just five times in 60 trips to the plate in May, so he seems to have gotten that under control. He should be a relatively high BABIP player in the long run, and the skills he has showcased lately make me think he will once again be a must-own player when that corrects. If he is available in your league, now is the right time to buy-low.