The striker, 26, was forced to sit out Rovers’ midweek trip to Blackpool as he served a one-game ban for his red card at AFC Wimbledon last weekend.
But the 22-goal top scorer will be restored to Doncaster’s line-up tonight when they host South Yorkshire neighbours Barnsley on Friday night at the Keepmoat Stadium.
“It’s nice to have a fresh John Marquis coming back into the squad,” said Rovers manager McCann. “That’s probably done him the world of good having a few days off.
“It was nice to give him a breather for a couple of days, take his mind off football, and re-focus.”
Rovers trained today, and McCann has no new injury problems after Blackpool, but could make changes with just 72 hours between games.
“Everybody is fine, everyone trained today, which is good,” said McCann.
“Everyone is looking forward to the game. Derby games are always one to look forward to, fans and everyone associated with the football club. It’s going to be a good game.
“The boys look fresh this morning, they look good. Everyone wants to play.”
McCann has been fined £1,000 and will serve a one-match touchline ban tomorrow after accepting FA charges for an incident which took place in the tunnel after Rovers' draw with Charlton Athletic at the Keepmoat Stadium.
Goalkeeper coach Paul Gerrard has also received a one-match touchline ban. Both will have access to the dressing room pre-match and at half-time.
McCann and Gerrard accepted the FA charges last week and learned the outcome at a hearing which took place on March 14. The sanctions are the minimum that could have been charged following acceptance of the charge.