The Chunichi Dragons of Nippon Professional Baseball re-signed Muller on Monday, Yakyu Cosmopolitan reports.
Muller pitched well in his first season overseas, posting a 3.42 ERA and 110:37 K:BB over 129 innings. The left-hander will remain in Japan for another season rather than attempt a return to the majors, where he's struggled to gain traction with a 5.90 ERA.