Zack Greinke’s lingering calf problem puts focus on Hyun-Jin Ryu

PHOENIX -- Zack Greinke has canceled his Saturday bullpen session because of lingering problems with his right calf muscle, a development that reduces his chances of pitching in the Dodgers’ season-opening series in Australia.

Greinke strained the muscle Thursday in his first start of the exhibition season. He was removed from the game after making only four pitches.

With Greinke’s status uncertain, the Dodgers could start Hyun-Jin Ryu and Dan Haren in their two-game set against the Arizona Diamondbacks in Australia on March 22-23.

The Dodgers were already considering the possibility of not starting Clayton Kershaw in the series as part of a plan to protect his arm. Ryu was mentioned as a likely candidate to step in for Kershaw, in part because he would broaden the event’s international appeal.

Ryu, who started his first exhibition game Friday, said through an interpreter he would pitch in Australia if asked by Mattingly. Haren is also on a throwing program designed to prepare him for the Australia series.

As for Greinke, he felt something when playing catch Friday with Stan Conte, the Dodgers director of medical services. That led to the cancellation of his Saturday bullpen session and made it unlikely he would take his next turn in the rotation on Tuesday.

“That doesn’t look very promising right now,” Manager Don Mattingly said.

Greinke would probably need three more exhibition starts to build up the arm strength necessary to throw 90 pitches in a regular-season game. Greinke could still pitch three more times this spring, but Mattingly said the Dodgers haven’t set a timetable for his return. He is scheduled to play catch again Saturday.

“The calf tells us when he can start doing the work,” Mattingly said.

Fortunately for the Dodgers, Ryu is in condition to provide adequate cover.

Unaware that major league players report to spring training already in shape, Ryu showed up to camp last year overweight. But he arrived in Arizona this year looking noticeably more fit. He said he wasn’t only in better cardiovascular condition, but also had a stronger arm than he did at this time last spring.

“It’s hard to come to our camp or be on our club and see what Kersh does and Zack does and not feel like, ‘Hey, maybe there’s something to do,’ ” Mattingly said.

Ryu limited the Chicago White Sox to two hits over two scoreless innings Friday.

Short hops

Matt Kemp underwent a routine MRI exam on his surgically repaired left ankle to determine how it is healing. In coming days, doctors will review the results and determine whether he can start running on anything other than a treadmill. … Josh Beckett is scheduled to start Sunday. The game will be the first for Beckett since he underwent surgery last year to relieve a nerve problem. … Carl Crawford, who missed two games with a strained thigh muscle, said he expects to return to the lineup Saturday. … Pitching prospect Ross Stripling underwent an MRI exam on his throwing elbow. Stripling felt tightness while throwing batting practice a week ago. The discomfort returned when he pitched in an exhibition game Thursday. He said the team’s medical staff thinks he has a strained ligament.

dylan.hernandez@latimes.com

Twitter: @dylanohernandez