Norwich City have released their official squad for the first half of the new season – opting to go two short of the 25 maximum.

Injured central defender Daniel Ayala, the summer signing from Liverpool who sustained a knee injury during the Carling Cup defeat by MK Dons last month, is not on the list.

The original diagnosis suggested Ayala could be out for 'a couple of months', but the 20-year-old does fall into the under-21 category – and clubs can use an unlimited number of under-21s in addition to their 25-man squad, which is why Jack Wilshere and Aaron Ramsey are not named in Arsenal's submitted list.

Canaries manager Paul Lambert has effectively got the use of every player on his books, apart from Oli Johnson, between now and the opening of the next transfer window on January 1, when a new list will be compiled.

The transfer deadline day departures of Stephen Hughes, Cody MacDonald and Anthony McNamee reduced his numbers, and although Johnson remained at the club, his omission suggests his future is away from Carrow Road.

There has been conjecture that manager Paul Lambert would add to his numbers, particularly at centre-half, where he has Elliott Ward and Zak Whitbread on his injured list, although they are expected to come back much sooner than Ayala – but Premier League rules allow him only to sign free agents.

The other area of interest was goalkeeper, where Lambert has lost the services of John Ruddy for the home game against West Bromwich Albion next Sunday after he was sent off at Chelsea nine days ago. Jed Steer is currently on loan at League One Yeovil and could be recalled.

Premier League rules state that alterations to the list can be made, but only in 'exceptional circumstances' – which could allow the manager to bring in an emergency loan. The other names not on the list, alongside Ayala and Johnson, are goalkeepers Declan Rudd and Jed Steer, midfielders Korey Smith, Josh Dawkin and Matthew Ball, and defender George Francomb – all of whom are under 21s.

The Premier League rules:

• Each club had a deadline of 5pm on September 2 to submit a squad containing no more than 17 players who do not fulfil the home-grown player criteria. The remainder of the squad, up to a total of 25 players, must be home grown.

• A home-grown player means a player who, irrespective of his nationality or age, has been registered with any club affiliated to the FA or the FA of Wales for a period, continuous or not, of three entire seasons or 36 months prior to his 21st birthday (or the end of the season during which he turns 21).

• Changes to the squad list of 25 may be made during the period of a transfer window or at other times only with permission of the board.

• U21 players are eligible over and above the limit of 25 players/squad.

• For the 2011/12 campaign under 21 players will have been born on or after January 1, 1990.