(Jonathan Newton/The Washington Post)

Seth Allen‘s otherwise promising freshman season came to a screeching halt Sunday, when the Maryland guard fractured a bone in his shooting hand during practice, Coach Mark Turgeon said.

Allen was defending Nick Faust around midcourt at the beginning of Sunday’s practice when he swiped for a steal and got his hand caught.

“I think it was reaching in. Next thing I know, he’s over on the sideline,” Turgeon said. “It’s unfortunate … I feel bad for Seth. He’s really been playing well. It’s a big blow to us, because of the way he’s been playing. But it just gives other guys opportunities to step up.”

The injury will keep him out of Tuesday’s National Invitational Tournament quarterfinals at Alabama, though Allen will travel with the team. He will see a specialist upon returning to College Park. If the Terrapins advance to the semifinals in New York City, Turgeon doesn’t expect Allen to be ready for that either.

A cast draped Allen’s left arm, which was wrapped in a sling during Monday’s practice in the Comcast Center auxiliary gym, but he seemed in good spirits, laughing and joking with teammates and shooting around with his right hand while wearing street clothes. He was not made available to the media.

“It was at the beginning of practice,” point guard Pe’Shon Howard said. “No one really saw it happen. You heard him screaming a bit. I thought he was going to be right back into practice. Then coach grabbed us, saying we make sure we take our subs in practice, because we wouldn’t have as many guards. Seth was out. I don’t think anybody knew how serious it was until after, but you could see he was in a lot of pain.”

Allen’s absence strikes a substantial blow to Maryland’s backcourt, where the Woodbridge, Va., native had excelled off the bench. Allen had reached double figures in five postseason games, and was the Terps’s third-leading scorer (10.8 points per game) during that span. He played a key role during Thursday’s win over Denver, using his deft dribbling skills to blow by defenders in isolation, one-on-one scenarios.

Despite largely serving as a sparkplug in a reserve role, Allen has been the most consistent of Maryland’s four freshmen, averaging 7.8 points and 2.2 assists per game this season, though his shooting numbers dipped during the ACC tournament (31.8 percent over three games). But Allen regained his form once the NIT began, shooting 54.5 percent against Niagara and Denver and averaging 14 points for those two games.

Aside from 11th man John Auslander’s fractured tibia and Allen’s recent injury, the Terps have been quite healthy this season. No regular has missed a full game due to injury. Only Howard has missed a full game altogether, and that was due to suspension (vs. Duke) and sickness (at Florida State).

“The thing where it hurts us, is we’ve been playing a small lineup a lot,” Turgeon said. “We can still play a small lineup, but maybe not as much. Guys like [James Padgett], Charles [Mitchell], Shaq [Cleare] will probably get those minutes also. We’ll see how the flow of the game goes.”

This is familiar territory for Allen. He broke the fourth metacarpal in his left hand on Dec. 26, 2011 during his senior season at Fredricksburg Christian.

>> Dez Wells and Logan Aronhalt also sat out Sunday’s practice with various nagging injuries. Wells landed hard on his knee during the ACC tournament, while Aronhalt has dealt with some lingering back issues. Both practiced fully on Monday, however, and are expected to be at full strength for Alabama.