Sunderland's £12million ace, who has scored three times already this season, has yet to tell manager Craig Levein he is willing to come back and play for his country after the pair's relationship broke down, despite Tweeting he would answer his country's call if asked.
McLeish said it was up to the 25-year-old to show the "cojones" to pick up a phone to Levein and make himself available, but one way or another the impasse between them should be addressed.
"Somebody could sort it out," said McLeish. "Life's too short, and in football management you need your best players.
"I don't know what the impasse is so it's not fair of me to say one way or another that Craig's wrong or Steven's wrong.
"It would be great if Stevie was only to make a phone call. Whether he's got the cojones to do that?
"Hopefully he has, because I'm sure he would want to play for his national team.
"If anybody can do it [play as a lone striker], it's Steven, but again I don't want there to be big critical headlines against Craig. It's just my opinion."
McLeish tried to sign Fletcher when he was boss of Birmingham City and Aston Villa.
"He grew in stature with Wolves over the last two seasons," said the ex-Gers gaffer.
"He was always a handful, strong in the air, he could take it in and he had good skill.
"And then he started scoring as well. He's started this season like a house on fire."