BOSTON — Pittsburgh sophomore guard Ashton Gibbs says he plans to remain in the NBA Draft and not return to school.“I feel I can play at the NBA level,” Gibbs said by text. “I’m looking forward to the challenge. When I entered the Draft, I entered to work my hardest to get drafted.” The 6-foot-2 Gibbs averaged 16.8 points, 2.4 rebounds and 2.4 assists for a Pittsburgh team that won the Big East regular season crown but was upset by No. 8 Butler, 71-70, in the second round of the NCAA tournament. Several top underclassmen have opted to return to school in recent days, including the North Carolina trio of Harrison Barnes, John Henson and Tyler Zeller and Kentucky frosh Doron Lamb. Ohio State frosh Jared Sullinger earlier said he would remain in school. Others, like Duke freshman guard Kyrie Irving and Arizona sophomore forward Derrick Williams, chose to leave early. The NBA faces an uncertain summer with a lockout looming if a new collective bargaining agreement cannot be agreed upon after the old one expires June 30. The NBA Draft is June 23 in Newark.