Securing the Bundesliga title this season had once looked like a foregone conclusion for Bayern, but their failure to win either of their last two league matches had seen Borussia Dortmund pile on the pressure.
Knowing that another poor result would complete their first three-match winless top-flight streak under Vincent Kompany, Michael Olise forced Oliver Baumann to tip over his powerful strike, before the hosts were rewarded for their pressure inside 20 minutes.
Kevin Akpoguma’s tug on Díaz in the area was judged to be enough for both a red card and a penalty, which Harry Kane duly dispatched to Baumann’s right.
But the personnel disadvantage appeared to only motivate Hoffenheim, who were superb in the lead-up to a richly deserved equaliser.
Ozan Kabak’s header wide and Fisnik Asllani’s striking of the bar both had Bayern hot under the collar, but Manuel Neuer remained casual enough to give it away cheaply to Asllani, who simply passed across the box for Andrej Kramarić to slot past the retreating goalkeeper.
That hard work was all undone, though, when Vladimír Coufal was the next to pull down Díaz just inside the box, and Kane stepped up once again, firing the spot-kick in the same place to restore the Rekordmeister’s lead.
That looked to be it for the first half, but there was still time for Bayern to break through in stoppage time, resulting in Díaz cutting inside and placing a right-footed finish past Baumann.
Asllani was denied by a reflex save from Neuer after the break, but Bayern were looking comfortable by now, and Olise passed it into the six-yard box for Díaz to divert in the hosts’ fourth.
Satisfied with that advantage, Bayern played it around with elegance in Hoffenheim’s half until late on, when Díaz struck into the far corner from the edge of the box, completing a superb first Bundesliga treble for the club.
The victory keeps Dortmund at arm’s length after their win over Wolfsburg on Saturday, as Bayern improve their H2H record with a fourth win in four since Christian Ilzer took over at Hoffenheim, scoring at least four times in each.
While not unexpected, it’s an abrupt end to Die Kraichgauer’s club-record five-match victorious Bundesliga run, but they’ll be pleased to get this fixture out of the way as they look for UEFA Champions League qualification for the first time in eight years.
Flashscore Man of the Match: Luis Díaz (Bayern Munich)