Tight end/wide receiver/H-back Devin Funchess committed to Michigan a little over a month ago. So far Rivals hasn't given Funchess a star rating. For comparison's sake, Scout gave him 4 stars and ranked him as the #6 tight end in the country. 247 Sports gives him 4 stars and rates him a 90 overall.
I've been a member of Rivals for a few years, and they often downgrade players without clearly defined positions. At 6'4" and 215 lbs. (or lighter), Funchess' future position is a little murky. Some think he'll develop into a full-fledged tight end, some think he might have the speed to play wideout, and some think he'll be an Aaron Shea-like fullback/tight end. Without knowing what position a certain player might occupy at the next level, it's difficult to say that he'll be a high-impact guy.
Also, keep in mind that the recruiting services figure in NFL potential with their ratings. Especially at Rivals, 5-star players are considered to be potential first rounders, 4-stars are thought to have good potential to be drafted, etc. Tight end isn't a premium position for the NFL, and H-back is even less so. Since 2004 the only two tight ends to receive 5 stars from Rivals were Martellus Bennett (2005) and Kyle Rudolph (2008). Consider that there were five 5-star running backs and nineteen 4-star running backs in the class of 2011. Meanwhile, there were zero 5-star tight ends and only sixteen 4-star tight ends in the same class. If the NFL doesn't value tight ends as highly as other positions, high school recruits are going to be slightly downgraded as a result.
So this is probably what Rivals is thinking:
a) What's his position at the next level?
b) Does he have a lot of potential to get to the NFL?
Personally, I think Scout and 247 Sports have it right. Putting on weight should never be a problem for a player who desires to do it, and I have heard no questions about Funchess' work ethic or coachability. I would rather take a good athlete and bulk him up than a take a big guy and try to make him more athletic. In my experience, the latter tactic will rarely pan out. Funchess can run, jump, catch, and adjust to the ball in the air. Michigan just saw a 2007 recruit who had similar size coming out of high school leave as a 6'4", 268 lb. tight end who excelled at blocking. But Martell Webb was a 4-star and the #29 wide receiver in his class, so you can see that the ratings aren't consistent. (I will admit, though, that Webb was probably a slightly better athlete coming out of high school than Funchess is today.)
Don't be too surprised if Funchess works his way up to 4-star status with a solid senior season. He has plenty of athleticism to move up to that next step, and if he remains on the 3-star level at Rivals, I think he'll outplay that rating by the time all is said and done.