However, Spurs boss Jose Mourinho confirmed that the defender has not suffered a setback and could be fit in time to face West Ham at the weekend.
Reguilon has not featured since the 3-1 win over Sheffield United a month ago, and in his absence Spurs have lost four of their last five Premier League games.
Tomorrow evening, they resume their European campaign against the Austrian side at the neutral venue of the Puskas Arena in Budapest – due to coronavirus travel restrictions – and when asked whether Reguilon would make the trip, Mourinho said: “No good news. He’s not coming.”
“No setback,” Mourinho added. “Just the process is not going as fast as initially we thought but no setback so let’s see. Weekend or next Europa League match on Wednesday. Let’s see.”