With Bayern trailing to a Joshua Kimmich own-goal midway through the second half and staring down the barrel of a second-successive European loss, Gnabry and Karl scored in quick succession to wrestle the match in Bayern's favour.

Gnabry set up defender Jonathan Tah for a late goal to ensure Bayern claimed all three points and rose to second in the league phase standings, behind Arsenal on goal difference.

Karl, 17, became the youngest player to score in three consecutive Champions League games.

Despite the loss, the Portuguese champions sit ninth in the 36-team table with two games remaining.

The first 24 sides make it through to the knockout rounds, with the top eight qualifying for the last 16 directly.

Bayern coach Vincent Kompany made seven changes to his starting XI, recalling Harry Kane, Gnabry, Karl, Manuel Neuer and Tah who were rested on Saturday against Stuttgart with Sporting's visit in mind.

Bayern have scored more goals than any other club in Europe's top-five leagues this season and went agonisingly close in the opening half.

Karl's fifth-minute goal was ruled out for offside and Kane hit the post on the half-hour mark. Kane, Karl and Gnabry all forced Rui Silva into acrobatic stops before the break.

Sporting's best chance in the opening half came when Geny Catamo laid on a precise cross which Tah almost guided into his own net, forcing Neuer into a reflex save.

Some more Bayern friendly fire put Sporting in front early in the second period, with Neuer this time helpless as Kimmich deflected a Joao Simoes cross in with 54 minutes gone.

The goal jolted Bayern into gear and the German side soon struck back to take the lead with two goals in four minutes.

Unmarked at the back post, Gnabry tapped in a Michael Olise corner to level things up. Karl latched onto a Konrad Laimer pass before blasting in on the turn from a tight angle.

With 13 minutes remaining, Kimmich and Tah made good on their defensive errors by combining for Bayern's third, with a little help from Gnabry.

Kimmich looped in a dipping cross to Gnabry, who headed centrally for Tah to poke home.

With three minutes remaining, Kompany withdrew Gnabry and brought Alphonso Davies onto the pitch, the Canada captain playing his first match since tearing his ACL in March.