Chelsea have been chasing Modric all summer and are ready to come in with a new £30million offer for the Croatian despite the imminent arrival of Juan Mata from Valencia.
Spurs have been clear in their declarations that they would not entertain offers for Modric, who covets a switch across London, but may now struggle to maintain that stance after Redknapp was forced to leave him out of the squad for his club's Premier League opener on Monday night.
Modric is not 100% fit but Redknapp may have been prepared to gamble on him had he been sure of the midfielder's committment to the cause.
Instead, he will play no part against the champions.
Redknapp told talkSPORT on Sunday: "He's got a little bit of an injury. There's a possibility he could have played through it. But at the moment his head's not in the right place."
That judgement is telling given that Arsene Wenger was prepared to play Samir Nasri - thought to be close to a switch to Manchester City - against Liverpool at the weekend.
Gareth Bale has called on the squad not to mourn the loss of Modric if he does leave White Hart Lane.
Bale, like Modric, had an outstanding campaign for Spurs last season, and does not want the 25-year-old to leave.
He does think, however, that the squad cannot dwell on his departure should he do so.
"Luka is a fantastic player," Bale said. "I'm not sure what the situation is with him but I think if he is here then he's great for the team but if he's not then we have to get on without him."
Spurs were without Modric and fellow midfielders Jermaine Jenas, Steven Pienaar and Sandro for last week's 5-0 Europa League qualifying win over Hearts match, but coasted to victory thanks partly to impressive displays from replacements Jake Livermore and Niko Kranjcar.
Bale was impressed with how the Tottenham squad coped against the Scots and thinks that bodes well for the team ahead of what promises to be a long season thanks to their participation in the Europa League.
"Luka and JJ (Jenas) didn't play so it gives confidence to the whole squad that we can play like that," the Welshman said.
"These players that came in are international players and they showed that they are all class. It shows what kind of squad we have got."