The Reds face a difficult trip to Tottenham this weekend with Rodgers' midfield options looking thin on the ground.
Gerrard's hamstring injury, sustained in Saturday's 4-1 win over West Ham, could keep him out until well into the new year.
Fellow midfielder Jordan Henderson has bruising on his right ankle from the tackle by Kevin Nolan which resulted in the Hammers skipper being sent off and has been wearing a protective boot to ease the pressure on the joint.
However, the 23-year-old is expected to be ready for the game at White Hart Lane which is also likely to see Lucas Leiva recalled in place of Gerrard having been dropped to the bench last weekend.
With Henderson, Allen and Lucas all expected to start against Tottenham that leaves little in the way of back up.
Summer signing Luis Alberto, who has made only seven substitute appearances in the Premier League totalling 113 minutes, is the only other player who could possibly do a job in the centre but he is more comfortable in an attacking role.
Central midfield, particularly in terms of defensive capabilities, is an area Rodgers has needed to strengthen and he may have to look at addressing that when the January transfer window opens.
Allen has now started back-to-back league matches for the first time since December 15 last year and is beginning to start showing a return to the sort of form which persuaded Rodgers to bring him with him from Swansea in the summer of 2012 at a cost of £15million.
"I've struggled with different injury problems but you'd hope that they're behind me now and I can focus on getting out there and playing more and more," Allen told liverpoolfc.com.
"The manager has just told me to be ready for when my opportunity comes and to get back to my best. That will come with game time. Nothing has changed really.
"But everything comes together with playing time, so I'm looking to getting a string of games and showing what I can do."
Ah it could be worse, I dont think Gerrard had the best season so far anyway, the last 3 games he played well but not outstanding at the start of season. He is going to be missed dont get me wrong, but its not the be all and end all. I am worried with Allen and the lack of replacement for these injuries, top midfielder and striker required in January. Its just a pity these injuries to Gerrard and Sturridge happened when we have Spurs, Chelsea and City all away from home. Massive few weeks ahead starting against Spurs, just hope their strikers are still forgetting how to score.- new1fowler_9