Kansas' Joel Embiid was the No. 1 center prospect regardless of Cauley-Stein's decision. Embiid is huge (7-foot, 7'5 wingspan) and has a soft touch around the rim. He can rebound and has the length and foot speed to develop into an NBA rim protector. But the center crop is blurry after Embiid.
Bosnian big man Jusuf Nurkic is a true center. He's a tall (6'11), powerful (280 pounds) scorer and rebounder, but he isn't nearly as athletic as Embiid. Indiana freshman Noah Vonleh is more naturally a power forward at this point. He can stretch the floor on offense and he's pretty quick for his size. At 6'9, he isn't as tall as Cauley-Stein, but he has a strong, mature physique and a gigantic, 7'3 wingspan. He isn't a great athlete or rim protector yet (2.1 blocks per 40 minutes), but he has the physical profile to one day play center.
Switzerland's Clint Capela is way too thin (211 pounds) to man the paint in the NBA right now. He really struggled defending the No. 1 high school prospect, Jahlil Okafor, at the Nike Hoop Summit. Okafor is NBA ready from a physical standpoint (6'10, 272 pounds) and he manhandled Capela on the block. Capella isn't physically ready to play in the NBA, but the frame is there. The Swiss big man is 6'11 in shoes and has a 7'4.25 wingspan.
Behind Capela is Baylor's Isaiah Austin. The sophomore big man is a true seven-footer with range to the three point line. But he's a beanpole (220 pounds) and that really hurts his ability to fight on the glass and in the post. After that, Florida's Patric Young is the best available, but he isn't worth a first round pick. Michigan State's Adreian Payne is, but he's way more comfortable at power forward than center.
Cauley-Stein is a natural center and his decision to return to Kentucky will likely hurt his draft stock. Next summer's draft class is loaded with big men at the top. He'll compete for position with Okafor, Kansas' Cliff Alexander, Kentucky's Karl Towns and Myles Turner (undecided). Cauley-Stein isn't as skilled as Okafor or Towns and he's two years older than Alexander and Turner. He could develop his raw post game next season, but if he leaves he'll already be 22 years old before the 2015-16 NBA season even begins.
That's before you take in account the competition for playing time he'll face in Lexington. Kentucky's front court is loaded and there's only so many minutes to go around. Kentucky freshman Dakari Johnson replaced Cauley-Stein in the starting lineup late in the 2013-14 season and he'll likely stick around for his sophomore season. Five star recruits Trey Lyles and Towns will need minutes, so will veteran forward Alex Poythress and Marcus Lee. Cauley-Stein only played 24 minutes a night this season and that number could actually drop in his junior season.
Ultimately, Cauley-Stein's decision to stay is exactly that: his. He loves UK and not being able to compete in the Final Four nearly killed him. For those reasons, it's impossible to blame him for wanting to return for another year of school. But that decision has major implications on the 2014 draft class and his stock next summer.