Defender Jamie McCombe scored the only goal of the game for Rovers in the 80th minute, but the Robins barely tested home goalkeeper Gary Woods.
MacDonald reckons his team can still win promotion and said: "We've got five games left and the aim is to win them all.
"Whether that will be enough to give us automatic promotion we'll have to wait and see but we are certainly capable of winning those games.
"Obviously we're disappointed with the result and the performance because we didn't play as well as we can do in this game.
"We didn't really get to grips with the game for whatever reason.
"I thought we might have got away with it and might even have pinched a win ourselves because we defended well but then we allowed their man a free header for the goal.
"It's too early to make judgements straight after a game and I'll be having a good look at the video of the match.
"The pitch didn't help but it was a case of getting our heads down and getting stuck in. There are one or two things we need to work on but it's important to stay positive and confident."