The game was being played nearly two months later than planned due to heavy snowfall causing the postponement of the original fixture in December, but that didn’t change the inevitability of Bayern bossing possession and Union staunchly setting up camp just outside their own penalty area.
The lack of final-third space meant the hosts had to knit quick, slick passes together to make any form of progress, and one such move saw Guerreiro’s low cross poked narrowly wide by Kingsley Coman.
Premium chances were hard to come by, however, and Bayern didn’t threaten again until Leroy Sane fired inches off target shortly before the break.
A wayward Janik Haberer half-volley was all Union had to show for 45 minutes of hard graft, but the away fans were undoubtedly happier than their Bavarian counterparts - some of whom booed as players headed back to the dressing room, letting Thomas Tuchel know they expected better in the second period.
The disgruntled supporters got what they wanted only 30 seconds after the restart, with Harry Kane thumping the post and Guerreiro skilfully turning in the rebound to leave the visitors fighting a daunting uphill battle.
Kane thought he’d grabbed his customary goal just a few minutes later after clinically converting Sane’s cut-back, but the VAR’s offside check had other ideas, setting up a nervy finish which included a convincing penalty shout against Konrad Laimer, as well as a touchline scuffle between Sane and Nenad Bjelica which saw the Union boss shown a straight red card.
Bayern are still firmly in the hunt for a 12th consecutive Bundesliga title, and only two more matches stand between them and a potentially decisive trip to Leverkusen on February 10th.
Union, meanwhile, have won only two of their last 22 matches, and they will be desperate to beat fellow strugglers SV Darmstadt 98 in a vital clash on Sunday.
Flashscore Man of the Match: Raphael Guerreiro (Bayern)
