Bale was carried off on a stretcher in the dying seconds of Thursday's 2-2 draw against Basel after David Degen stood on the 23-year-old's standing ankle.
Sometimes injured players have to wait over 24 hours before swelling subsides so the injury can be scanned accurately, but it is understood that is not the case with Bale, who will have an assessment on the ankle on Friday .
A Tottenham report on the 22-goal forward's injury last night described the Welshman as being in "severe pain" because of the tackle, which occurred in stoppage time of the Europa League quarter-final first leg.
Bale's right ankle was positioned almost at a right angle to his leg because of the challenge, but Tottenham manager
Andre Villas-Boas was confident his star man would make a quick recovery on Thursday.
He said: "Gareth will definitely play again this season. "We will know better (on Friday) but I'm pretty confident.
"From the medical department's first analysis, everything is positive.
"It shouldn't be as bad as it looks because Gareth has torn that ligament before and there's nothing to tear now."
Aaron Lennon and William Gallas, who also had to come off last night with knee and calf problems respectively, will also have scans on Friday.
The injury worries could not come at a worse time for Tottenham, who are battling Arsenal, Everton, and Chelsea for the final two Champions League spots.
Villas-Boas is already without Younes Kaboul (knee), Jermain Defoe (pelvis), and Sandro (knee) for Sunday's crucial Barclays Premier League game against the Toffees at White Hart Lane.