From Rotoworld:

An undisclosed team joined the Blue Jays, Nationals and Pirates as finalists for free agent Tomo Ohka with a bid made on Sunday.
Ohka is expected to make his decision by the end of the week. The Mets, Mariners, Red Sox and Diamondbacks previously had interest in Ohka, but the mystery team isn't necessarily from that group. It's especially unlikely that either Boston or Arizona made a late bid. The Astros, Cardinals, Reds and Giants could all use one more starter and might be candidates.