Whittaker, who originally signed with the Arizona Cardinals as an undrafted rookie in 2012, rushed for 71 yards and a touchdown on 13 carries in Sunday night's 28-16 victory over the Kansas City Chiefs. He also caught one pass for 22 yards.
Reaves, an undrafted rookie, rushed for 19 yards and a touchdown in the exhibition opener against Buffalo.
Whittaker and Reaves showed a tough, physical running style that the Panthers look for in their ball control offense. Barner didn't. He had 1 yard on eight carries in the opener and 18 yards on seven carries in the second game.
A sixth-round pick out of Oregon, where he played for current Eagles coach Chip Kelly, in 2013, he also struggled in pass protection.
Barner was competing as a kickoff and punt returner as well. But the Panthers want to give undrafted rookie wide receiver Philly Brown a hard look as the punt returner and there are others equally capable of returning kickoffs.
Getting a seventh-round pick was a bargain since Barner likely wouldn't have made the 53-man roster.