The 6-foot-8 North Carolina native flashed some moments of brilliance last season, such as when he went off for 20 points and seven rebounds when Louisville stormed back to crush Syracuse in the Big East championship game at Madison Square Garden.
But now Harrell is training with the USA U19 team in Colorado Springs, Colo., battling some of the top bigs in college basketball.
"Yes, because there's a lot of good guys out here," Harrell told SNY.tv by phone. "There's a lot of great bigs out here that's really competing and we're really getting after it so I really think this will improve my game."
Harrell has been battling Shaq Goodwin of Memphis, Jarnell Stokes of Tennessee and Jerami Grant of Syracuse, among others.
"I'm out here and really working hard so I can fill the spot of Gorgui Dieng," said Harrell, who averaged 5.7 points and 3.6 rebounds.
The 26-man camp will get cut to 12 in time for the 2013 FIBA U19 World Championship in Prague June 27-July 7.
Florida's Billy Donovan is the head coach, and VCU's Shaka Smart and Virginia's Tony Bennett are assisting.
Looking ahead to next season, Kentucky and Louisville are projected to be two of the top teams in the country and the in-state rivals will meet at least once -- Dec. 28 at Rupp Arena. The teams have won the last two NCAA championships and one of them could win again this year.
"Yeah, I'm really looking forward to playing them," Harrell said. "Everybody thinks that they're going to be really good because they have a couple guys coming in, but they don't really know what we have coming in and that's what we want, so we're just going to get out there and compete."
He added: "We're just looking at it as another game that we have to get and we gotta get the win."
With everything Louisville has coming back, Harrell believes Louisville can reach a third straight Final Four.
"I think we can," he said. "If we get the new guys to buy in and really work hard and get after it, I really think that we can go back-to-back [with national titles]."
For now, Harrell's goal is simply to make the U19 roster.
"It would mean a lot," he said. "This is a great group of guys. There are a lot of strong guys here and I'm just honored to be invited back here."
And if he makes the team, he said, "It's a blessing."
**For more stories on the USA U19 & U16 teams, click here.