Whelan, who won six league titles during his Anfield career, believes Benitez's decision to substitute striker Fernando Torres after an hour of the Reds' 3-1 defeat to Fulham - when the scores were locked at 1-1 - was proof the Spaniard has his eye on Europe.
The Reds face Lyon away on Wednesday night, and Whelan told Ireland's RTE Television: "It's all gone wrong with the manager and he's shown exactly where his priorities lie. He wants to win the European Cup so he can get a job in Europe."
The defeat at Fulham slipped the Reds nine points behind Premier League leaders Chelsea, and Whelan believes Benitez may not see out the season in charge.
"For me, his days have got to be numbered at Liverpool," he added.
"He's taken players off who are the only players who are going to give you a chance of winning the game.
"And he drags them all off because he's got a game on Wednesday.
"When I saw the team I thought he's not bothered about this game. He's putting all his eggs in one basket and I can't see why he's done it."