RICHARD Foster sees no reason why his old gaffer Derek McInnes can't go toe-to-toe with Celtic and mount a sustained Premiership title challenge with former club Aberdeen.

The Rangers full- back worked with McInnes at Bristol City as he saved the Robins from relegation to League One in season 2011-12.

He was sacked two years ago this month with the club sitting bottom of the Championship.

But Foster is delighted at how McInnes has rehabilitated his reputation at his hometown team.

He said: "Winning the League Cup last season was great for him and they are doing well this season.

"It's good that there is competition in the top league and judging by their results, I don't see why Aberdeen can't keep it going.

"They have a lot of quality and I'm sure if they do go on a good run then Celtic will have to look over their shoulder."

Foster added: "When I went down to Bristol we were bottom of the league and he got us out of it. We won our second-last game of the season and that was enough for us to stay up. The second season we started really well.

"We beat Cardiff and Crystal Palace who actually went up that year, but we went on a bad run and found ourselves in a bad situation.

"I was of the view Derek would have done what he did the previous season and get us out of it. But owners in England want to protect their investments and it is their right to make a change where they see necessary."