Aston Villa’s turbulent season took another turn for the worse with Roy Keane delivering a bolt from the blue by announcing that he would be leaving his role as assistant manager with immediate effect. Keane informed Paul Lambert of his decision barely 24 hours before Saturday’s crucial fixture at Burnley. With another critical game on Tuesday, at Crystal Palace, followed by Leicester City’s visit on Sunday week, the timing could hardly be worse for Lambert.

Keane said that he made the decision because he was finding it impossible to combine his role as No2 at Villa with his position as the Republic of Ireland assistant manager. Ireland, however, do not play until March and it seems odd that Keane should choose such a hectic period, at a time when Villa are struggling and Lambert is coming under growing pressure, to walk away from the position he accepted in July, when he replaced Ian Culverhouse.

There have been rumours that Keane was involved in a bust-up with a player but Lambert has denied that was the case. The Villa manager, who has seen his side pick up only two points out of a possible 24, is now looking for his third assistant manager in six months and, with Keane’s decision to quit totally unforeseen, an appointment is unlikely to be made until after the trip to Selhurst Park at the earliest. Steve Clarke, who has been out of work since being sacked as West Bromwich Albion head coach last year, could be a potential candidate.

In a statement on the Villa website, Keane said: “Ultimately, my roles with Villa and Ireland and combining my commitment to these have become too much. It isn’t fair to either Villa or Ireland, so I’ve made this decision. I’d like to thank Paul for giving me a great opportunity to come to a brilliant football club. I’ve really enjoyed my experiences at Villa and I wish the management team, the players, the supporters and the club nothing but the best going forward.”

Lambert added: “Roy came to me this [Friday] morning and he informed me that, ultimately, the difficulty of combining both roles has prompted his decision, which I respect totally. In the brief period we have worked together he has been great in the role and I understand his reasons for leaving.”

In another development, Lambert has admitted that Villa may consider selling Fabian Delph in January. His contract is up at the end of the season and the England international, who is recovering from shoulder surgery, has indicated that he wishes to keep his options open, leaving Villa with the choice of trying to cash in when they can or hold on to the player for the remainder of the season because of his importance to the team.

Asked if Delph could be sold in the transfer window, Lambert said: “For people going into the last year there is always that case. You are never sure what can happen. With the Bosman ruling the player holds the cards. I know that because I’ve done it myself. The main thing is to get him fit. That’s the main objective, to get him going again because he was playing ever so well. Once we get him back fit, I’m pretty sure he will be ready to go and we will see what happens.”