The 26-year-old netted once to lead the way for Bayern, taking his tally for 2015-16 to 13 goals in 14 Bundesliga appearances.
Muller's goal saw him equal his Bundesliga record of 13 goals in one season and Sammer has been thoroughly impressed with the Germany international's performances.
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"Thomas is irreplaceable. He is an absolute role model for Bayern, a person everybody can identify with," Sammer was quoted as saying by AZ.
"Thomas knows what Bayern means and what this club represents. He is both confident and humble.
"A lot of teams would love to have a player like Thomas in their team. He is a real gem.
"We are pleased that he still has a lengthy contract with Bayern."
Bayern went 11 points clear of second-placed Borussia Dortmund following Saturday's win, with Thomas Tuchel's men taking on Stuttgart on Sunday.