Shinji Okazaki struck twice and set up another to spark Mainz to a 3-2 victory over Hamburg SV on Saturday.
With Mainz down 1-0, Okazaki equalized in the 47th minute and three minutes later, set up Nicolai Muller to give the visitors the advantage.
Rafael van der Vaart made it 2-2 for the hosts on 79 minutes, but Okazaki had the last laugh by completing his brace in the second minute of injury time.
"When I first got here, I was hesitant and things didn't go well for me at times but I'm glad I stuck it out," Okazaki said. "Initially, I had a target of scoring five goals this season, but now I want more."
Okazaki, along with Muller, leads his club with eight goals for the season so far.
Mainz's win pushed them up to ninth place on 24 points, 20 behind leaders Bayern Munich, who lifted the Club World Cup on Saturday with a 2-0 victory over Raja Casablanca in the final.
Mainz manager Thomas Tuchel sung his striker's praises, saying Okazaki had it in him all long.
"I have always been convinced by Okazaki's ability, and his recent production underlines that," Tuchel said.