MIDDLESBROUGH will be forced to field a makeshift back four again this weekend, after both Chris Riggott and Ugo Ehiogu were ruled out of Saturday's trip to Southampton.

Riggott missed Monday night's 3-2 win over Manchester City after suffering a hamstring injury in training and, while the problem is not serious, it will take at least a week to heal.

The centre-half has been one of Boro's most reliable performers this season, with Monday only the second time he has missed a Premiership game.

Boro's medical staff expect him to be fit for next week's crunch UEFA Cup clash with Partizan Belgrade, but Saturday's trip to the south coast will come too soon.

Riggott's injury looked like opening the door for Ehiogu but, despite returning to training last week, the England international will not feature at St Mary's either.

A series of niggling problems have restricted Ehiogu to just three first-team appearances this term, with his last outing coming in October's Carling Cup win over Coventry.

That win came at a cost, with the former Aston Villa defender suffering a recurrence of the calf problem that had plagued him in the previous two months.

His rehabilitation has progressed to the running stage, but Steve McClaren will not risk his recovery by throwing him back into first-team action without a prior run out for the reserves.

With two of his leading centre-halves sidelined, the Boro boss will again be forced to rely on veteran Colin Cooper as his side look for their fifth away win.

Cooper's time on Teesside looked to be at end when he was loaned to North-East neighbours Sunderland in March.

But, after being recalled to the Riverside after just two weeks, the 37-year-old has provided valuable cover this term.

He started UEFA Cup games in both Banik Ostrava and Egaleo, and will be making his fourth Premiership start at Southampton this weekend.

August's defeat at Arsenal marked his 400th Boro appearance and, while his current playing deal expires in the summer, the Durham-born defender remains as committed as ever.

"You know Colin's going to run through a brick wall for you," said skipper Gareth Southgate, who played alongside Cooper on Monday. "He's inspirational to play alongside.

"I don't want to harp on about his age because I wouldn't like it myself, but when you see someone of that age perform with such enthusiasm and desire to win, it has a great effect on everyone around him."

* Middlesbrough defender David Wheater has been included in the England Under-18s squad for this month's friendly with Scotland.

Goalkeeper David Knight and midfielder Danny Reed are on standby for the game, which will take place at Hartlepool's Victoria Park on Wednesday, December 22.