The Twickenham crowd are sure to bid an emotional farewell but Cohen, who has been named on the bench, believes his England colleague should not be hanging up his boots just yet.
"Jason is a phenomenal player and he's had a wonderful career," said Cohen.
"I sent him a text a few weeks ago when I agreed to play in the game saying how proud I'd be to play alongside him.
"I'm sure Twickenham will give him a standing ovation but I don't think he should be retiring.
"He has got one or two more seasons left in him. Mentally I think he's a little bit fuzzed.
"I hope he ends up missing the game and comes back, but I don't think he will. It's up to Jason. He likes his family time."
Cohen will be the beneficiary should Robinson's troublesome shoulder cut short his final hurrah.
The 29-year-old winger has not played since the end of last season following his acrimonious split with Northampton and the breakdown of his planned move to Leicester.
The earnings from his testimonial year would have seen the Tigers break their salary cap had they signed him and he has been stranded in limbo since September.
However, negotiations to end his exile are at an advanced stage - Leicester still appear the likely destination - and should be completed within the next two weeks.
But next on the agenda is Saturday's appointment with the world champion Springboks and Cohen is relishing the chance to lock horns with Bryan Habana.
"I'm not nervous about the Barbarians. I'm just looking forward to having the next run-out," he said
"I feel a lot fresher for the break I've had. Rugby is a brutal game and that's what we love about it.
"But now I've been getting up and my body doesn't hurt. That's been quite refreshing.
"Any break will prolong a rugby player's career. Players don't get enough time off.
"I've been away a while but hopefully my body will remember how to absorb the shocks.
"It will be good to get a half for the Barbarians. I haven't played for a while so wasn't expecting to start.
"But I'm looking forward to facing the best winger in the world at the moment - Bryan Habana. He's phenomenal. His all-round game is brilliant."