Bale's agent Jonathan Barnett had said on Wednesday the Wales winger was "towards the end of his career", after Tottenham manager Jose Mourinho had questioned the player's Instagram post suggesting he was in good health despite being unavailable for Spurs' FA Cup defeat at Everton last week.
A wonderful individual strike from Lucas Moura extended Spurs' first-half lead, and although Michael Liendl pulled one back for the Austrians with a second-half penalty, the English club have one foot in the next round after Carlos Vinicius' 88th-minute goal. Mourinho has never lost a knockout tie in the competition, which he won with Porto in 2003 and Man United in 2017.
AC Milan, who have not reached the quarter-finals of any European competition since the 2011-12 Champions League, had to settle for a 2-2 draw at Red Star Belgrade. Milan, who face Inter in a top-of-the-table Serie A derby on Sunday, were pegged back as Milan Pavkov netted a dramatic 93rd-minute leveller for Red Star, who played the closing stages with 10 men.
Patrik Schick scored twice as Bayer Leverkusen fought back from three goals down only to lose 4-3 to Young Boys in Bern, while Olympiakos beat PSV Eindhoven 4-2 in Piraeus.
Dinamo Zagreb edged out Krasnodar 3-2 in Russia and Edin Dzeko's early goal helped Roma to a 2-0 win at 10-man Braga.
Standout matches today