It was recently reported that Gibson has not yet signed on to reprise his role as Aaron 'Hotch' Hotchner for the CBS drama's seventh season, with just three weeks remaining until production begins.
Mantegna, who plays David Rossi, has now told TV Line that he feels "confident" Gibson will be back.
"I certainly hope [he'll return]," said the actor. "I feel confident... that they'll work it out. It'll all be what it'll be."
Mantegna also praised departing Criminal Minds star Rachel Nichols (Ashley Seaver), who was recently dropped from the series.
"She did a great, great job and… she's going to do just fine," he said. "She's a young actress, so she's got her whole career ahead of her."
It was previously confirmed that Paget Brewster will return to Criminal Minds for the seventh season, while A.J. Cook will also reprise her role as JJ full-time.
Criminal Minds's seventh season will air on Wednesdays at 9/8c on CBS in the fall.
> Criminal Minds star teases series changes