McMahon said: "As a supporter and an ex-player I'm frustrated beyond belief. I know about all the off-field problems but it's gone on longer than that.
"I went to the Birmingham game at Anfield in September and I was excited because I wanted to see Fernando Torres play. I've not been so disappointed in a long time when I found out he was on the bench. The crowd were so subdued. I'd never known Anfield so quiet. I want to see the best players play. You can understand it if Liverpool are winning all the time and he tinkers a little bit.
"Torres is a goalscorer, a fantastic player. He wants to be the leading scorer in the Premier League. He wants to be the best at his job. I'd be mega-frustrated if I wasn't getting the opportunity every game."
Liverpool trail league leaders Manchester United by 17 points and McMahon added: "Cristiano Ronaldo plays every game. You don't see Sir Alex Ferguson leaving him out or Wayne Rooney or Carlos Tevez when it comes to the big games.
"You need to have partners - Rush and Dalglish, Keegan and Toshack, Ronnie Whelan and me, Jan Molby and me, Hansen and Lawrenson. You can go through all the teams and name the partnerships. You can't name them for Liverpool at this time. I don't know who Steven Gerrard is going to play with from one week to the next. I don't know who Torres is going to play with.
"The combinations now are all different . There's never any consistency in the pattern of play. You can change it on the periphery, the wide players maybe. But the spine of the team should be the same. Rafa is a very good coach but I think he's more suited to the European game. I like him and have no doubts about his coaching credentials but I just think he's shortchanging people at times. If I was a paying spectator I'd want to see Gerrard and Torres playing every game.
"They have problems now because you have to ask if Liverpool are going to make that fourth place. Financially, it's a must. It's February, they are seventh and they have a very tricky period coming up.
"They can't make excuses. They're professionals and what happens off the pitch shouldn't affect them. They can still do well in the Champions League but they should be staying in title contention a lot longer."