"I don't think Geo has got anything to prove (to City) whatsoever. He's a fantastic player and from what I can gather they really enjoyed him at Manchester City," the veteran striker said.
"Geo is our Robinho, as it were. I'm sure it'll be a great game and I'm sure Geo will do well. Hopefully, he'll score the winner.
"Not many people score winners against Manchester United, so that's the mark of the player.
"But the biggest thing that stands out for me is his work rate. If you've watched our games week in, week out he's been a fantastic team player. He's a match-winner and a great guy and we all love having him around.
"You need players like that; he's worth his weight in gold."