Paul Lambert's mounting injury list took a turn for the worse when Stephen Hughes went under the surgeon's knife.

The Scotland international underwent exploratory surgery to get to the bottom of an ankle injury that has bugged him since pre-season – and almost certainly means an extended spell on the sidelines for the 27-year-old midfielder.

It also officially removes one more option for City manager Lambert, whose resources are starting to be stretched – emphasised by a first appearance for 17-year-old Academy starlet Matt Ball on the bench against Crystal Palace on Tuesday night.

Lambert's midfield choices have also been diminished by a knee ligament injury to Andrew Surman sustained in early September, which will sideline him until December, while Tom Adeyemi is spending the rest of this year on loan at League Two Bradford City.

Owain Tudur Jones and Matt Gill, who have figured infrequently under Lambert, are due back from loan stints at Yeovil and Peterborough respectively before the end of the month. But it remains to be seen whether the City boss sees them as cover for his steadily depleting squad.

'Stephen is going for an operation on his ankle; that's another one that will be out for a bit of time,' Lambert admitted to the BBC on Tuesday night.

The Norwich manager is also down on defensive numbers – although the return of Elliott Ward for Middlesbrough's visit to Carrow Road on Saturday will be a boost. The centre-back served a one-match ban against the Eagles for picking up his fifth booking of the season at the weekend draw with QPR.

But left-back stalwart Adam Drury has been ruled out for 'a few weeks' with a calf injury sustained at Loftus Road, while centre-backs Michael Nelson and Zak Whitbread are still some way from being involved after lengthy injury lay-offs.

Young defender George Francomb is on loan at Barnet until early next month, while striker Cody McDonald is Lambert's remaining missing man, as he spends the season on loan at Gillingham.

With central defender Leon Barnett the only player currently brought in on loan by Lambert – from West Brom until January – another dip into the loan market could yet tempt the City boss.

• Senior players available for Saturday (21)

Goalkeepers: John Ruddy, Declan Rudd, Jed Steer. Defenders: Russell Martin, Leon Barnett, Jens Berthel Askou, Elliott Ward, Steven Smith, Sam Habergham. Midfielders: Wes Hoolahan, Korey Smith, Simon Lappin, Andrew Crofts, Anthony McNamee, David Fox, Josh Dawkin. Strikers: Grant Holt, Chris Martin, Simeon Jackson, Oli Johnson, Luke Daley.

• Players unavailable (10)

Defenders: Michael Nelson (ankle, due back next month), Zak Whitbread (calf, no return set), Adam Drury (calf, two to three weeks), George Francomb (loan, Barnet, due back November 7).

Midfielders: Andrew Surman (knee, due back around Christmas), Stephen Hughes (ankle, no return set), Tom Adeyemi (loan, Bradford City, due back in January), Matt Gill (loan, Peterborough, due back end of October), Owen Tudur Jones (loan, Yeovil, due back end of October). Strikers: Cody McDonald (season long loan, Gillingham).