"Christian Dailly is out of the Christmas programme with suspected pleurisy," he confirms.
"It is a major blow because as captain he is an influential figure, but we have defensive options with Robbie Stockdale able to play right back if Tomas Repka goes back to central defence and also Hayden Mullins can play at the back.
"Christian is having tests and will have an antibiotic to get the fluid off the lungs."
Michael Carrick should be okay to return at the weekend after missing the Sunderland game with a gash - he required stitches at half time against Stoke - while Neil Mellor could return to the squad after, like Steve Lomas, coming through a reserve team friendly at Charlton earlier in the week.
Alan denies making a move for Darren Huckerby at Manchester City as has been reported, and adds:
"Much as I like Huckerby there is no way I will be bringing him to West Ham.
"I have good strikers at the club who can score goals, and, just like Kevin Keegan's Manchester City when they went up, I can bring on good forwards from the bench, as I did on Saturday, if I need to.
"Jermain is a massive player, make no mistake, but I repeat that he is totally focused at West Ham and that is all we can ask.
"Everything else is hypothetical and not worth talking about, to be honest; he is always going to be looked at as he is a top player.
"Saturday's win was about the team, though, and he played his part."
One of those striker substitutions that Alan feels will make a difference in games showed his value on Saturday in Brian Deane, who came off the bench to set Jermain up for a goal with his first touch.
"I brought him here because he has been there and done it; he knows what it takes to get promoted out of this division and the little things he says help," says Alan.
"He doesn't speak loud and jump up and down but as he showed on Saturday he is passionate in his performance and is a nice steadying influence on the place."
Meanwhile, the away trip to Reading and the Madejski Stadium on April 3rd will be shown live on Sky with a 12.30pm kick-off.