Spurs have made a fine start to life among the elite of European football by taking four points from their opening two games to lie joint top of Group A alongside Inter.
But manager Redknapp fears failing to add to that total in their mouthwatering clashes with the reigning champions on October 20 and November 2 will ultimately prove fatal.
He told Spurs TV Online: "We've had a good start, we've played well in Germany (against Werder Bremen) and we had a great win last week (over FC Twente).
"But it's still going to be tough. That group is so tight.
"You've got two games now with Inter Milan; you've got to get some points from those games, because the other teams are going to pick up points now.
"If we don't have a good spell, Inter Milan could be through and then the last couple of games, they go and put reserve teams out because they've already qualified.
"That's how the Champions League goes. If you're a betting man and wanted to have a bet, the last games are impossible (to call), because half the teams don't bother.
"They've already won their group, or they can't come any better than second."