We begin our series of Controversial Prospect Updates with a look at Twins lefty Tyler Robertson, who is either one of the best southpaw prospects in A-ball, or just a guy with a weird delivery who will fail in Double-A and/or get hurt at some point.

First, the statistical breakdown.

Robertson is 4-2, 2.76 in 11 starts for Class A Fort Myers in the Florida State League, with a 58/22 K/BB ratio in 65.1 innings. He's allowed 63 hits. He has a1.79 GO/AO ratio and has given up just three homers. He's holding left-handed hitters to a mere .157 average, possibly due to that weird delivery in combination with his breaking stuff, but right-handers are hitting him at a .301 clip. The raw numbers are pretty similar to what he did last year in the Midwest League (2.29, 123/33 K/BB in 102 innings, 87 hits), although not quite as good. Some of that is the difference in competition, and at age 20 Robertson is age-appropriate for the FSL. Walk rate is not significantly different, but the strikeout rate is down and he's been more hittable, 1.30 WHIP vs. 1.17 last year. So statistically there is a bit of slippage but overall he's still pitching quite well.

Kiley McDaniel over at Saberscouting has an in-depth scouting report about Robertson that is a must read. McDaniel includes some video of Robertson's unusual delivery. Weird mechanics don't scare me as much as they do some people, as long as the guy repeats them well and his body is used to them. That seems to be the case with Robertson.

What does concern me is the loss of velocity: his fastball was anywhere from the mid-80s to the lower-90s last year, but has settled back into the 80s without touching the higher readings this season from what I've heard. That's a red flag, and combines with the mild-but-there ratio deterioration to make me worry that he may very well hit a wall in Double-A.

Of course, he's still just 20, and his numbers are still very good. If I were the Twins, I think I'd leave him at Fort Myers the rest of the year. Pushing him to Double-A seems quite risky to me at this point. I gave him a Grade B+ in the book this year, and in retrospect that does look too high. I am lowering him to Grade B for now. That could go down another notch depending on what happens in the second half.