Former Scotland striker Andy Gray has warned Manchester United that they could be missing out on a "once-in-a-lifetime" opportunity if they do not appoint Jose Mourinho as their new manager.

Mourinho has been heavily linked to the Old Trafford post since his departure from Chelsea, with incumbent boss Louis van Gaal under increasing pressure following a run of six games without a win.

The Dutchman's future was reportedly the subject of a board meeting this afternoon, further intensifying speculation that he could be on the verge of the sack, and Gray believes that a lack of other world-class alternatives will make United turn to Mourinho sooner than they otherwise might have done.

"I see Mourinho as the only one of the top three or four managers in the world available. You look at the really top names and [Carlo] Ancelotti has gone [to Bayern Munich], Pep Guardiola looks set for Manchester City. Would anyone else be big enough come in? I don't see anybody," Gray told talkSPORT.

"The fact that Jose is available has probably rushed them into doing something. I think if Jose was still at Chelsea then Van Gaal would would get little bit more time to sort it out but this might be a once-in-a-lifetime chance to get Mourinho, at the right time, into Manchester United. I think there is every chance it could happen.

"Louis is overseeing a club and a side that are not playing with a smile on their faces. I don't get the impression the players are enjoying it, I know the fans aren't enjoying watching it, and there is one of the best coaches in world football sitting on his backside, twiddling his thumbs right now. Why wouldn't one of the biggest clubs in the world be interested in one of the best managers in the world?"

One report has claimed that Mourinho has already signed a five-year deal with United, while others suggest that defeat to Stoke City on Boxing Day would spell the end of Van Gaal's tenure.