The Hammers slipped to a 3-0 Barclays Premier League defeat at the Stadium of Light with James Collins limping off in agony with a grade three hamstring tear to join George McCartney and Joey O'Brien on the sidelines.
Allardyce clinched a six-month loan deal for Brazilian striker Wellington Paulista on Friday but will now turn his attention to his back-four after seeing his patched-up rearguard succumb alarmingly on Wearside.
He said: "The big blow for me is not having enough defenders at the moment. There are too many of my defenders injured.
"We have had too many injuries recently but the injury situation with defenders with George McCartney not being here, Joey O'Brien not being here and James Collins getting injured means the defensive side of our team is particularly weak and short of numbers now. I am really going to have to go and try to strengthen that area in the next few days."
Sunderland went ahead after 12 minutes when Sebastian Larsson smashed home a left-foot piledriver, his first goal of the season, and they never looked back as the Hammers succumbed with barely a whimper.
Adam Johnson doubled their advantage within two minutes of the restart when he cashed in on Dan Potts' error and James McClean made sure of the points with a third 16 minutes from time after Stephane Sessegnon, not for the first time, had terrorised the visitors' defence.
Allardyce, who saw his side only just fail to beat Manchester United last weekend, was particularly concerned about the comedy of errors which led to the second goal, which effectively killed off the game.
He said: "Just look at it, it was pathetic, wasn't it? We have a free-kick and we let the opposition score. [Keeper] Jussi [Jaaskelainen] gets us out of jail in the first place by making a really, really good save and then we mess up the clearance and they score, so it probably sums us up. We didn't defend correctly, we didn't have the appetite for defending correctly and nullifying the opposition's strengths, we never passed the ball as well as we know we can.
"It was really an all-round performance that makes life extremely difficult for me to accept, the performance I have seen based on how well we played just seven days ago against Manchester United. The level of difference in performance between that game and this is just staggering. All round last week, we were absolutely brilliant in all departments; this week, we were poor in all departments, hence we were beaten comprehensively by a team who deserved to beat us."
- Sports & Recreation
- Wellington Paulista
- George McCartney