The Seagulls thumped Chelsea 3-0 on the night with the performance described as "unacceptable" by manager Liam Rosenior.
Cahill told Sky Sports: “I said before it was a huge game and one they needed to win and they just got totally outplayed, there are no positives you can take from that game.
“I feel somewhat for Liam, I feel the players let him down, but there are some unpleasant stats out there about Chelsea and they are some tough times ahead.
“And Sunday's FA Cup semi-final is now pivotal for this club, but they look fragile, low on confidence, fragile and in all honesty, it was a difficult watch to be fair.
“The last 20 minutes, they almost accepted their fate, second to every ball and they were just miles off it tonight.
“To be seen to be giving a lack of effort, there is no excuse for that. The last 20 minutes especially, I was watching that thinking they’ve given up. They’ve accepted that they’ve lost the game and that is the worst thing.”