Vedran Corluka believes Harry Redknapp has been guilty of not rotating his squad enough this season and would not be surprised to see Tottenham finish sixth in the Premier League.
Spurs enjoyed a stunning start to the campaign as they managed to keep pace with Manchester City and Manchester United, and at the very least looked set to qualify for the UEFA Champions League.
However, despite at one stage being 12 points clear of third-placed Arsenal, Tottenham are now fifth in the table following a dismal run of one win in their last nine matches.
Redknapp maintains that a top-four finish should be viewed as an extraordinary achievement, rather than something which should be expected of the North London club.
Corluka disagrees, though, and says it must be regarded as a disappointing season for Spurs if they miss out on a return to the Champions League.
"Tottenham, for me, had one of the best teams in England and of course it will be an unsuccessful season if they don't go to the Champions League," said the Croatian, who is on loan at Bayer Leverkusen.
"I don't know what the chairman will do if they don't qualify. I know only that it will be an unsuccessful season.
"Three months before they were in the title race challenging City and United.
"Now they are three points behind fourth spot. They are fifth and it's going to be really difficult for them."
Corluka thinks the main reason behind Spurs' collapse has been the fatigue of their star players after Redknapp's refusal to rotate.
The idea worked towards the end of 2011, when Spurs went on an unbeaten 11-match run, but the run of consecutive games has left the likes of Scott Parker, Kyle Walker and Benoit Assou-Ekotto looking tired of late.
"I wouldn't be surprised if they finished sixth," Corluka said.
"They didn't rotate enough. They don't have depth on the bench.
"That's the main problem. I watched almost every Spurs game and they played them all with the same 11, 12, 13 players and that's why the players now are really tired."