Newcastle United have just eight games remaining to save themselves from relegation.
Benitez was given just 10 games to save Newcastle, and he has failed to win either of his first two matches at the helm.
The former Real Madrid lost to Leicester City in his first match in charge, before drawing 1-1 with Sunderland yesterday.
And although Carver believes that Benitez is exactly the right man for Newcastle, he fears that the club may have kept hold of Steve McClaren for too long.
“It’s going to be very difficult,” Carver admitted. “I think it’s a fantastic appointment - possibly the biggest one since Sir Bobby Robson. But I think it might be a bit too late.
“We have to win at least four games, and we’ve only won six all season. We do have four winnable games - at home to Crystal Palace and Swansea and then away to Swansea and Aston Villa. If I was Rafa, I’d be thinking they are winnable.”
Newcastle are currently sat in 19th place in the Premier League table, and they are three points adrift of safety.
Their chances of staying up are becoming slimmer by the game, but things could have looked even bleaker had they not rescued a point against Sunderland in the derby.
Newcastle were behind for a large portion of the match at St. James’ Park, but Aleksandar Mitrovic came to the rescue by scoring a header in the final 10 minutes of the contest.
Newcastle’s next match comes against fellow relegation strugglers, Norwich City, on 2nd April in what looks like a hugely important game for both side’s seasons.