Tottenham managed to hold on to Modric this summer despite receiving at least three offers for the Croatian, the biggest reported to have been £40million.
Despite pleading to move to Stamford Bridge, Modric remained at White Hart Lane, and he has since gone on to play a big part in helping the club go on the 11-match unbeaten run which has catapulted them to third in the Barclays Premier League.
"We won't be selling our best players or anyone we want to keep in January," Redknapp said.
"We are keeping our best players and if anything we will be adding to the squad not selling.
"That's the message from me and the chairman. We won't be weakening this squad. If one or two positions open up where fringe players want to go then we will look at that but we are not going to sell our best players or anyone we want to keep."