Was left hopelessly exposed by Boateng's mistake as Mainz stole a shock lead. Had to be on his toes in the second period too as Nicolai Muller and Choupo-Moting both stung his palms.
What should have been a straightforward, uneventful afternoon for the centre-back was ruined by one moment's lapse in concentration as he misjudged the long ball that allowed Parker in to open the scoring. Will have been grateful there were no real repercussions.
Still revelling his deep midfield role, the captain didn't have too much mopping up to do as Bayern controlled possession. Continued to burst forward with the ball at his feet though when the opportunity arose.
Saw a large amount of the ball in the opening half as the home side looked to exploit the right channel. Was sacrificed at half-time for the arrival of game-changer Gotze.
Could have easily been mistaken for Fellaini in a Bayern shirt considering how far up the pitch he was playing in the first half as the home defence sat on the halfway line. Had to come off though after a bruising tackle with Pospech.
Didn't really have the opportunity to get involved in the opening period as Guardiola's sacrificed width on the left to accommodate Muller in the team. Appeared down the right in the second half though and had a hand in the second goal.
Frustrated by an efficient Mainz defence in the opening period. Quickly began to find space after the introduction of Gotze and took his goal superbly while also laying on Muller.
Couldn't find the key pass to pick the lock of the visitors' defence in the opening period. Took a back seat when Gotze came on and changed the game.
Grew frustrated at his side's failure to break down a deep-lying Mainz defence in the opening period, letting fly with meaningless long-range efforts. Like his team-mates though, found the gaps eventually and was in the right place to win the penalty.
Billed as left midfielder, Muller had no intention of getting chalk on his boots as he immediately moved in field to link up with Mandzukic. Fruitless in the first half, but sticking around up top led to his two goals, even if he did have to snatch the ball off Robben for the penalty.
Exasperated after the lack of service in the opening stages, the Croatian was brought into the game much more after the break and showed his clinical prowess with his finish for the third.
Conceding four goals was certainly harsh on Wetklo, who produced a number of quality stops, most notably from Schweinsteiger's volley, and couldn't be put at fault for any of the goals.
Didn't turn up for the second half, his mind must have still been in the changing room as he kept Robben onside as he knocked home the equaliser and things only got worse from there.
Slotted in as a third centre-back as the visitors looked to shut out their opponents. Successfully kept Mandzukic at bay in the opening period, getting the better of their aerial duels, but was undone once Bayern found space on the ground.
The Danish centre-back has been part of Mainz side that has one at the Allianz in the past, but it wasn't to be on this occasion as a promising defensive display quickly went to pieces with the arrival of Gotze.
A busy afternoon for the Costa Rican as he stood up to Robben down the right. Heavily outnumbered and outfoxed in the second period, the first three goals all came down his flank.
Had a fairly easy time of it in the opening half as Bayern focused their efforts through the middle and down the right. Came off his wing to clatter into Dante and was repaid by being forced to deal with his replacement Alaba for the duration of the second period.
A disappointing display from the Bundesliga's top scorer as he went missing for large parts. Only tested Neuer once from the edge of the area, but was slow to support Parker on occasions.
Looked dangerous as Mainz threatened to break on occasions in the first half. Produced the deliveries for a couple of well worked training ground routines but unfortunately no end product came of them.
Fantastic vision to place Parker through for the opening goal, although there was more than a hint of luck with the ball reaching the forward only thanks to Boateng's mistake.
Blew a fantastic chance to draw his side level as he put a free header wide when the scores were still at 2-1. Worked hard apart from that though to make a mark at both ends.
Took his goal really well as he pounced on Boateng's mistake to round Neuer and give Mainz the lead. Didn't have many chances in the second period and was subbed despite looking visibly buoyed by the goal.
Came on for the injured Dante and was put to use on the left to give the hosts a bit more width that was evidently lacking .
A special moment for the forward as he came on to face his former club but he only came away with a booking to show for it.
As 45 minute cameos go, this is up there. The midfielder came on to make an instant impact, setting up two goals and playing a big hand in a third. He hasn't started much for Guardiola's side due to injury but this performance will see him shoot up the pecking order.