Richardson and Kirkpatrick announced they would not return for their senior seasons with the national champions on Thursday. Alabama spokesman Jeff Purinton said Hightower also isn't returning.
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Richardson and Kirkpatrick are both projected as potential top-10 picks while Hightower is regarded as a potential first-rounder.
Richardson won the Doak Walker Award as the nation's top running back and was third in the Heisman voting. He set single-season rushing records at the school with 1,679 yards and 21 touchdowns.
He and Hightower, a linebacker, were first-team AP All-America selections while Kirkpatrick, a cornerback, was a second-teamer.
The Tide lost three underclassmen to the NFL last year, but wound up beating LSU 21-0 in Monday night's national title game. Kirkpatrick and Richardson were part of two national championship teams.
Richardson said he made the decision Wednesday night. He went home to Pensacola, Fla., from the national championship game in New Orleans to discuss his future with family.
He said he wanted to be able to take care of his mother -- who he says has Lupus -- and two young daughters.
"This place has changed my life," Richardson said. "It really turned me from a teenager to a man, and a grown man at that."
Hightower was eligible for a fifth year after missing most of the 2009 national championship season with a knee injury. He wasn't present at the news conference, and Saban only talked about Richardson and Kirkpatrick.
He said both players pledged to complete their degrees and are about 20 credit hours shy. Hightower, a team captain, graduated in December.
"The chance to be a key part of our national championship team this year made for the perfect end of my Alabama career," Hightower said, via the school's official site. "I can't thank coach Saban, (Alabama defensive coordinator Kirby) Smart and the entire coaching staff enough for helping mold me in the player and person I am today."
Outland Trophy Award-winning left tackle Barrett Jones had already announced he's returning for his senior season.
The Associated Press contributed to this report.