Midfield ball-winner Muntari was sent off three times and collected eight yellow cards last season for Italian club Udinese, who sold the 22-year old Ghana World Cup star to Pompey for a reported £7.2 million last month.

And Redknapp is worried his dismissal following a second bookable offence against champions Manchester United - just a minute before Cristiano Ronaldo was also red-carded for aiming a headbutt at Richard Hughes - could signal a nervous time ahead.

He will miss Saturday's home clash against Bolton with a one-match ban after tripping Ronaldo early in the second half and then going in late on United's Michael Carrick.

And Redknapp admitted: "Muntari is stretching into challenges and has got to watch it. The first foul was an innocuous trip on Ronaldo but he should have been more careful with the second one.

"Referees in the Premier League will pick up on that and often they can't take account of over-enthusiasm.

"I think Sulley has a big future here but he has to be a bit more careful with his challenges."

Regarding the red card shown to the Portuguese, Redknapp said: "I didn't know why Ronaldo was sent off. I couldn't see but the referee was right there, wasn't he. I'm surprised because Ronaldo's not that type of boy is he?"

United boss Sir Alex Ferguson accused Portsmouth of "intimidation tactics" in the 1-1 draw, but Redknapp who, at 60, is the second-oldest manager in the Premier League behind the Scot, said: "It was just a typical Portsmouth performance - a fantastic performance. I haven't spoken to Alex.

"Our injuries were so many that I ended up with a back-four entirely made up of left-footed players and that's a bad balance.

"But the boys - including Pedro Mendes and young Martin Cranie who I took off at half time to make tactical changes - all did so well."

Skipper Sol Campbell missed out with a groin injury, right-back Lauren picked up an ankle problem in training and Noe Pamarot, who deputised for Campbell, came off after 66 minutes with a pulled hamstring.

Redknapp said: "They are not all ruled out for Saturday just yet but they are all struggling.

"Linvoy (Primus who had an outstanding season at centre-back last year) is still miles away at the moment after his knee operation and we could be down to just the 16 fit players."