Despite giving the matter consideration, Latics elected not to appeal Wesolowski's red card for kicking out at Scunthorpe's Damien Mozika during Tuesday's 2-2 draw and the midfielder must now begin a three-match ban.
In the same match, winger Montano suffered a torn thigh muscle and boss Paul Dickov fears a lengthy lay-off.
"He's going to get a scan on Friday," he said. "At the minute it's looking as if it's going to be weeks rather than days. We just need to get the scan done to get confirmation of how long he's going to be."
Robbie Simpson returns from suspension and is expected to feature in midfield alongside Dean Furman - the Oldham skipper playing his final game before departing to represent South Africa in the African Nations Cup.
With an eye on the midfield shortage and the congested fixture list his squad have endured in recent weeks, Dickov took the precaution of only allowing eight players to train on Thursday morning, including two goalkeepers.