And the Buddies manager has refused to rule out the defender returning from cruciate ligament damage before the end of the season.
McGregor was ruled out for the entire 2012/13 campaign when he suffered his second cruciate injury in as many years in a game against Hibs last August.
However, the 27-year-old is making excellent progress in his rehabilitation and has started running at the Saints' training complex in Ralston.
Lennon reckons seeing his team-mates beat Celtic at Hampden to reach the League Cup Final last month has lifted the player in his battle to regain full fitness.
He said: "Darren is doing very well. He is out running and hopefully he'll be doing some light training come the end of the month.
"He is doing very well physically and mentally. I see no reason why he can't get to a stage where he can be in contention to play games. I am sure he will have enjoyed seeing the boys getting to the cup final.
"Of course, there will be disappointment that he cannot be involved.
"But all of the players become supporters of the club whenever they are not involved and are pleased to see us doing well and lifted by it."
Lennon added: "Tommy Reilly is also doing well in his rehabilitation. He has the plaster off and is working hard to build up the muscle in his calf and other areas.
"Apart from our long-term injured, we have a fully fit squad at the moment for the game with Aberdeen this weekend. "