Along with Arsenal, the two sides are battling to qualify for next season's Champions League.
The Spurs boss told Sky Sports News: "It will be extremely difficult, but if we achieve these nine points we will be enjoying Champions League football next season.
"That is our aim, but we understand that other teams are improving and it will probably go down to the wire.
"We didn't play well in the first half [against Southampton], but we deserved the points after what we did in the second half. It was not the 'Spurs way', but in the end it keeps us in the frame and hopefully we will improve, and play better against Chelsea. It's a big, big game."
The teams meet at Stamford Bridge on Wednesday evening.