The 31-year-old England captain had been battling a calf injury picked up in Bayern's Champions League clash with Celtic five days earlier, managing only a brief training session before the Frankfurt showdown.
Expecting to sit out entirely, Kane surprised fans by taking a place among the substitutes. "I didn't train much after Celtic, just rested it as much as possible," he told reporters post-match. "I tested it for 30 minutes yesterday, and it felt decent. We decided today I'd be on the bench - it was the right call.
"Fresh legs were key, and that's what we got."
Bayern boss Vincent Kompany opted to start Thomas Muller up top, leaving Kane itching to get involved. "I hate watching when I'm not playing, I don't enjoy it," Kane admitted.
He finally entered the fray in the 64th minute, replacing Muller, and got 20 valuable minutes to test his recovery. "It felt good out there," he added. "With five days until Friday's game, I'll get treatment and be ready."
The Bavarians, who face Stuttgart next in the Bundesliga, were relentless against Frankfurt. After a sluggish start, they broke through in first-half stoppage time when Michael Olise tapped in from Leroy Sane's cutback.
Hiroki Ito doubled the lead on the hour mark, punishing a blunder from Frankfurt keeper Kevin Trapp, before Jamal Musiala and Serge Gnabry sealed a dominant display.
The victory stretched Bayern's lead at the Bundesliga summit to eight points and marked their 10th straight home league win.
Kane praised the team's energy, crediting the rotated squad. "We suffocated them without the ball, tons of fresh players made the difference. It was a top performance," he said.
Bayern's X account echoed the sentiment, posting: "A statement win at the Allianz Arena, pure dominance."
Looking ahead, Kane's sights are set on a Champions League last-16 clash with Bayer Leverkusen on March 5. The teams have already met three times this season, two draws in the league and a 1-0 cup loss to Leverkusen. "They'll be tough games," Kane predicted. "They beat us once and will fancy their chances again. But if we bring today's energy, we can hurt them. It'll be exciting."
For now, Bayern are flying, and Kane's cautious return only adds to their momentum as they chase silverware on all fronts.