The Irn-Bru First Division pacesetters meet at Cappielow for a top-of-the-table battle that could see Allan Moore's side open up an 11-point advantage in the title race.
The Jags have played three fewer games than the Ton and saw fellow hopefuls Dunfermline lose more ground in a midweek loss to Cowdenbeath.
Defeat for Thistle will not end their dreams of clinching the championship, but former Firhill keeper Rough admits it is far from an ideal situation.
He said: "Unfortunately Thistle are now chasing. It is always good to have the points on the board.
"There is a bit of pressure on now. If they had played their games, they could have been on level points and, for talking's sake, if Morton won then they would only be three ahead.
"If Morton win on Saturday there will be a massive gap, although Thistle will have the games in hand.
"Psychologically, I think things have swayed a bit towards Morton.
"The Thistle boys will be looking to win and then get talking about the games in hand. It is swings and roundabouts.
"Morton are doing well and their confidence is high, but I was here before a lot of the games got postponed and I was impressed with Thistle.
"I was impressed with Chris Erskine and Steven Craig will score goals at any level for you.
"Neither of the teams are that much better than each other, it will be down to which team turns it on on the day."
Saturday's Cappielow clash will be the first time Thistle have taken to the field since boss Jackie McNamara left for Dundee United.
It has been a frustrating few weeks for interim boss Alan Archibald, but Rough is confident the uncertainty over the Jags' top job won't affect Thistle's football focus.
"I would like to think that the players would be professional enough to know these things happen in football," he said.
"I don't know what the situation will be with the manager and if the boys will be given until the end of the season or they will bring someone in.
"There is nothing worse being in a dressing room not knowing if the two guys in charge are going to be with you all the way or if you will get a new manager in. You have got to have some stability. I am sure the people in charge will have spoken about it and the players will know what the situation is."
Key to Thistle's chances this weekend will be the form of keeper Scott Fox, with the Jags shot-stopper looking to record his first clean sheet of the campaign against the Ton.
Rough said: "Thistle were successful while he was playing then he got an injury.
"Like any keeper, when you are out for a long time, you get a back four that are used to you being there and it can knock you off balance when he is not there.
"The injury hindered him a bit, but the more games he gets in the run-in will help and he will certainly be a big player for Thistle this weekend.
"He has had a taste of the SPL at other clubs and, like every player, I am sure he will want to get back there and it will be one of his ambitions."