Smith, through tears, remembered Allen as a "good dude," a "great player," and a "super person" in a clip he posted to his Instagram page just minutes after the Dallas Cowboys revealed the former offensive lineman had died Sunday while on vacation in Mexico.

Smith played with Allen from 1994 to 2002 ... and while he said he hadn't been able to see much of the Hall of Famer following his retirement, he was still obviously shaken.

"My thoughts and prayers go out to his family," the former running back said. "My heart is just broken."

Smith rushed for a record 18,355 yards in his career -- and Allen paved the way for most of them. The two clearly grew close through their time together -- and after Allen died, Smith implored his followers to never take people for granted.

He then called Allen "a beast" on the football field ... but a man with "a big heart" off of it.

"He will be sorely missed," Smith said.

The ex-Dallas tailback was hardly the only one eulogizing Allen on Monday ... Troy Aikman also sent his thoughts and prayers in a post on X, writing, "He was a HOF offensive lineman that dominated opponents regardless of the position played. Off the field, he was a gentle giant that loved his family. Rest in Peace LA."

Added Hall of Fame President Jim Porter, "[Allen] could literally beat the will out of his opponents, with many quitting midgame or not dressing at all rather than face him, but that was only on the field. Off it, he was a quiet, gentle giant."

"Our thoughts and prayers are with his wife Janelle; daughters, Jayla and Loriana; and son, Larry III."

Allen was just 52 years old.