Modric has been the subject of sustained interest from the Blues this summer and, despite Spurs repeatedly declaring they would not entertain offers for the Croatia playmaker, Chelsea still seem determined to get their man.
Redknapp told talkSPORT: "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."
The imminent arrival of Juan Mata at Stamford Bridge does not appear to have deterred Andre Villas-Boas, with another bid in the region of ?£30million expected this week.
Although Redknapp is loathe to part with Modric it would provide him with major funds to add to his squad, something he is eager to do before the end of the month.
He added: "We'll get one or two players in before the window closes. The chairman is very close to doing a couple of deals. If we can get a couple of players in we'll look even more quality. It will improve us again.
"You have to keep improving because all the other teams have gone out and improved. Liverpool have done it. Probably only ourselves and Arsenal haven't done too much."
Source: PA
Source: PA