Heynckes has been a revelation since being brought in earlier this season for a fourth spell in charge, keeping the Bavarians on course for another famous treble.
The 72-year-old has made clear that he does not intend to stay on beyond the summer, however, despite the best efforts of Bayern's board to tie him down for 12 more months.
"Tuchel has the quality to coach Bayern," he is quoted as saying by ESPN. "I rate Thomas Tuchel. He has continued the progression from the youth teams at Mainz. That is the stairway to success that you must take, learning the correct approach and people skills.
"Under Tuchel, Borussia Dortmund played excellent football with a good system -- all of today's modern footballing elements were there for everyone to see.
"Tuchel's side finished runners-up, won the DFB Pokal and played attractive football. I had fun watching BVB, that's why I respect and rate him as a very good trainer."
Tuchel was sacked by Dortmund last year, three days after winning the club's first piece of silverware in five seasons, due to a rumoured falling out with the hierarchy.