"Probably the best way to describe left field, that [spot] is going to get contributions from more than just one player there," said Red Sox manager John Farrell. "Obviously Chris Young is going to be in left field at times. We've got Brock Holt out there today. Travis Shaw is another possibility. Rusney is an important guy for us. But to say that there's going to be 150 games played there by Rusney is probably a little aggressive at this point."
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In Sunday's 9-4 win over the Mets, Castillo went 1-for-3, including a single against the electric right arm of Noah Syndergaard.
"It's a good test," Castillo said. "I've tried my best to be productive in that kind of situation every time I'm up at home plate. Against a pitcher like him, it's good to be able to have those at-bats."
Castillo is hitting .273 in Spring Training with one extra-base hit in 33 at-bats. In 309 career at-bats since signing a seven-year, $72.2 million contract, Castillo is a .262 hitter with seven homers and a .680 OPS.
"I worked a lot on my spring this offseason and it feels good to get more reps and more practice at the plate," Castillo said. "This spring has been a pretty productive one from my point of view."
What will the Red Sox look for from Castillo in the final two weeks of Spring Training?
"To continue to progress with his approach at the plate," said Farrell. "I think he's done a solid job here in camp. He missed some time early, but he's caught up to speed. There have been some at-bats where he's shown an improved approach, almost aggressive selectiveness on his part. And that's the thing he spent time in the offseason with [hitting coaches] Chili [Davis] and with Vic [Rodriguez] honing even further."
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.