Masahiro Tanaka will rehab his partially-torn ligament.
Masahiro Tanaka will rehab his partially-torn ligament. (USATSI)

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Yankees ace Masahiro Tanaka has seen three different doctors, general manager Brian Cashman said on a conference call Thursday (via Yankees.com), all of whom said he has a partially torn ulnar-collateral ligament in his right elbow. None of the three recommend Tommy John surgery, though, the club announced, so instead Tanaka will have a platelet-rich plasma injection and rehab for six weeks.

If this doesn't help him recover, Tommy John surgery would then be a possibility.

The tear is said to be very small, in the 10 percent range, reports Jon Heyman.

This is a still serious blow to the Yankees, though. The 25-year-old right-hander is 12-4 with a 2.51 ERA (159 ERA+), 1.01 WHIP and 135 strikeouts in 129 1/3 innings this season. The Yankees are 13-5 in games he starts and headed into Thursday night 33-39 when he doesn't start.

CC Sabathia and Ivan Nova are already out for the season while Michael Pineda is also on the disabled list.

That leaves the healthy members of the Yankees rotation as Hiroki Kuroda, Brandon McCarthy, David Phelps and Shane Greene.

Tanaka signed a seven-year, $155 million deal with the Yankees this past offseason, and the Yankees also had to pay a $20 million posting fee to the Rakuten Golden Eagles -- Tanaka's NPB club.

After an amazing start to the season (11-1, 1.99 ERA), Tanaka has gone 1-3 with a 4.25 ERA in his last four starts.