He said: "Sol has been solid, absolutely solid.
"We have had two or three games this season which we haven't been proud of but, in fairness, apart from City, defensively we've been as good as we were last season. Recently we've been very, very strong and a big part of that is down to Sol. He will be a key figure again in Europe.
"A return to the England set-up has been mentioned and at the moment he certainly isn't doing himself any harm. If he's playing regularly in the Premier League and playing well then why shouldn't he put himself in the window?
"As far as I am aware, he's never retired. England might say the centre of defence is a strong position at the moment. Matthew Upson came in and did particularly well in the two games he played when John Terry dropped out.
"But I'm a big fan of Sol. It was he who got me to move to Portsmouth and he's playing very, very well at the moment. Sol's maintained his form from last season when we broke clean-sheet records, defensive records and whatever else.
"He's still a big player for us now."