Injuries to George Boateng, Mark Viduka, Ugo Ehiogu and Chris Riggott have added to the manager’s worries in recent weeks, leaving captain Gareth Southgate desperately trying to hold things together in defence with Tony McMahon playing his part and fellow teenagers Matthew Bates and David Wheater standing by.

Boro have been linked with moves for Celtic’s Bobo Balde and Juventus defender Igor Tudor in the last few days, but seem unlikely to get their hands on either in a difficult January market.

McClaren told the club’s official website, www.mfc.premiumtv.co.uk: “I think we’re short of cover at centre-half – indeed the spine of the side has been affected – but finding players at the moment is horrendous.

“It has become very frustrating, not just the transfer market which has been quiet for a lot of clubs, but it’s the fact that major injuries have disrupted our season after we were going so well.

“These are injuries which we could do nothing about. For instance, we thought Ugo would be a big player for us in the second half of the season.

“But what everyone has to do is just take a step back and look at the overall situation. We had a terrific first half to the season and the players we have working for us now are doing their best to stick in there.

“We know when these injured players return, we have a terrific squad. But we’re still looking, still enquiring and we have people recommended to us every day.”

The Teessiders remain in sixth place in the Barclays Premiership table after Saturday’s 4-4 draw at Norwich in which they led 4-1 with just 10 minutes to go.

They remain on course for the top-six finish they have set as their target for the season, but having looked like potential challengers for a top-four spot, find themselves seven points adrift of Everton heading into Saturday’s FA Cup round trip to Manchester United.

But McClaren is hopeful that, with key additions before the transfer window closes on Monday, he can lay the foundation for another push.