Matt Costello has never been your prototypical NBA Draft prospect. He's tall at 6-9, but undersized at the center position he played in college and not athletic or a good enough shooter to be considered a forward in today's NBA. You won't find him on any mock drafts on the reputable draft sites out there.
If Costello is going to make the NBA, he'll have to most likely do it the hard way: going undrafted, playing in the summer league, and making a roster during training camp. He was just invited to play in the Reese's College All-Star Game over the weekend, which is reserved for the best seniors in the country. He was unable to play in the game due to a minor back injury, but did participate in practices leading up to the game on Friday. He'll play in the legendary Portsmouth Invitational Tournament - another event for seniors - later this month.
One of Costello's greatest attributes as a player is that he plays to his strengths and doesn't try to be anything he's not. That's backed up by his 56.7% field goal percentage for his career. He took the majority of his shots at the rim and made over 70% of those shots during his senior year. He's never been a low post wizard, but he gets a lot of easy ones due to the fact that Costello had the highest offensive rebounding percentage in the Big Ten. Costello had the most total rebounds in the conference, despite the fact that he averaged just under 23 minutes per game.
Costello's biggest strengths lie on the defensive end. He had the second-best defensive rating of any player in the Big Ten this past season and was third in defensive rebounding percentage, according to Sports-Reference. While he's not an elite shot-blocker, Costello was still in the top-ten of the league. He consistently has done well limiting some of the better centers in the league.
It's hard to find a spot in the league as a 6-9 center without much of an offensive game. Scoring around the rim becomes much more difficult and without a great low-post game or a serviceable jump-shot, there's not a lot of ways to score. At times Costello showed the ability to knock down a mid-range jumper and even knocked down a couple of three-pointers, but they often came when he was wide open and he needs a lot of time to get the shot off. It's encouraging that his shot's not broken. Many players have developed into good shooters after their college years and Costello's 75% free throw shooting shows that he's at least got a repeatable form.
Referring back to his size and his athleticism and overall game, it's difficult to find a position for Costello in the NBA. He wouldn't be the first 6-9 guy at his size to play center, but he'd need to continue to be an elite-level rebounder.
It would be a surprise to see a team use a pick on Costello in the NBA Draft, but if he plays well in Portsmouth and in the summer league, it wouldn't be shocking to see him in an NBA training camp somewhere. Odds are in favor of him spending next year overseas, however.