Modric has been at the centre of a summer-long tug-of-war between Spurs and Chelsea, but the Croatian was given a warm welcome by the club's supporters when he came on as a first-half substitute during Tottenham's 2-1 win over Athletic Bilbao at White Hart Lane on Saturday.
Chelsea are said to be mulling over whether to return with an improved offer of over ?30million, but Redknapp still insists he will not be sold.
He said: "We are not going to sell our best players, the likes of Modric and (Gareth) Bale. We're looking to sell some fringe players but we have had no takers."
Spurs first-team coach Joe Jordan lavished praise on Modric after the game.
Jordan is convinced that if Modric does start the season with Spurs, he will be totally committed to doing his best for the club after making a good impression from the bench on Saturday evening.
"He is an exceptional professional," Jordan said.
"Whatever is going on in his mind, I can honestly say that it has not affected his approach to training.
"You can see today that he is in good condition.
"It (his performance) was typical of the player and the person that he is. He is a great lad. He is a good pro and a nice person.
"I think the players and the public appreciate him as a football player. But in the dressing room the players appreciate him as a person and a football player."
Redknapp has been linked with a host of players, including Emmanuel Adebayor and Lassana Diarra, but so far has only been able to bring in Brad Friedel and youngsters Cristian Ceballos and Souleymane Coulibaly.
The 64-year-old admits he is not been able to add as many players to his squad as he would have liked - a problem exacerbated by injuries to key players like Sandro, William Gallas and Ledley King.
"It's difficult. We would have liked to have got some signings before we came back," Redknapp said.
"We have a few injuries in midfield. Tom (Huddlestone, who has been struggling with injury) came in and had half a game today.
"If we don't get anyone then we will just carry on with what we got and see how we go."
Steven Pienaar joined that injury list on Saturday when he hobbled off after 24 minutes with a groin problem.
"He might have torn his groin," Redknapp said. "I think we're going to take him to a specialist and have a look at him. We'll see how it goes."
Spurs fell behind to a Mikel San Jose opener in a drab first half in which the home side looked well off the pace.
The introduction of the likes of Gareth Bale and Jermain Defoe at half-time gave the hosts the boost they needed and they eventually ran out 2-1 winners thanks to goals from Peter Crouch and Defoe.
Source: Team Talk
Source: Team Talk