Striker McDonald headed an equaliser seconds after Chris Porter had given the home side the lead on the hour mark.

And Georgios Samaras nodded in the winner from close range with 11 minutes left from Celtic's first corner - after Motherwell had failed to seriously trouble Artur Boruc from 11 of their own.

McDonald said: "Results are all that matter. If anyone says we didn't deserve to win it, I couldn't really care less.

"It doesn't really matter anymore. It gets us a little bit closer to the end."

The victory put Celtic eight points ahead of Rangers, who now have four games in hand.

McDonald told Setanta Sports: "It was a massive game, anything less than a win would have ended our title hopes.

"It was a terrific, battling performance. Motherwell stuck to their guns and made it difficult for us but in the end, we ground it out.

"Motherwell were right up for it, right in our faces and got a few of us upset. But we managed to calm ourselves down.

"We were a bit frustrated going in at half-time. They probably had the better patches of the game but the second half was a lot better.

"We went one down but we got one as soon as possible and that deflates them a wee bit."

Motherwell boss Mark McGhee was angry with referee Steve Conroy after the decision that led to Celtic's winner.

Hoops defender Bobo Balde headed out under pressure from Porter but Conroy gave a corner and Motherwell conceded their eighth goal from high balls into the box in just three games.

"We deserved something out of that game," McGhee said. "I think we weren't helped by one or two refereeing decisions.

"It was a massive decision for us because we know it's our Achilles heel, so we want to avoid corners.

"I could clearly see it was a goal-kick from where I was. I thought it was a really, really poor decision that put us under pressure and ultimately led to the winning goal."