BOSTON -- With a forecast of moderate to heavy rain expected throughout the evening, the Tigers-Red Sox series opener was postponed on Monday and will be made up as part of a day-night doubleheader on Tuesday.

This will give ace Chris Sale one more day of rest as the lefty attempts to snap out of the toughest early-season slump of his career.

• Sale plays catch ... in the concourse?

Sale will pitch the first game of the split twin bill, which will start at 1:05 p.m. ET. Tickets for Monday’s game will be good for admission for Game 1.

“I don’t think he’s anxious,” said Red Sox manager Alex Cora. “I think he’s ready."

Hector Velazquez will start Game 2 at 7:10 p.m. ET, filling in for Nathan Eovaldi, who will have surgery to remove loose bodies in his right elbow, according to a source.

All eyes will be on Sale when Game 1 begins. In his first four starts this season, Sale is 0-4 with an 8.50 ERA.

The issue for Sale in his first two starts was a lack of velocity, but he struggled with his slider his third time out. In his last start at Yankee Stadium, Sale had his best fastball of the season and a sharp slider, but he missed location several times.

“We had two different opinions of his [last] outing,” Cora said. “He felt like he disappointed himself and his family. I think that he’s close. Stuff-wise, he was great. He just misfired a few pitches and they took advantage of it, but I think he’s very close to taking off. Velocity was there, slider was there, the delivery was more consistent. I know he wants to get on the mound, but I think it’s just like a regular day for him.”

As for Velazquez, he has done a nice job swinging back and forth between the rotation and the bullpen for the Red Sox the last couple of seasons.

In 13 career starts, Velazquez is 2-4 with a 4.09 ERA. Cora said the 30-year-old Velazquez will likely stay in the rotation for at least the next two turns.

Injury updates
Infielder-outfielder Brock Holt, who has made inconsistent progress from the scratched cornea in his right eye, might be ready to ramp up activities again. Holt was pulled off his Minor League rehab assignment last week after just one game.

“Brock, he’s going to hit [in Boston] tomorrow. He didn’t do it today. He’ll hit here tomorrow and see how he feels,” said Cora.

There was also some news on lefty Brian Johnson, who is out with left elbow inflammation.

“B.J. actually starts playing catch tomorrow or the next day at 60 feet,” said Cora. “I saw him today. He had a smile on his face. He’s feeling a lot better.”

Emerging bullpen force
Righty Marcus Walden, who didn’t make the Red Sox out of Spring Training but has already been called up from the Minors twice this season, is turning into a high-leverage weapon for Cora.

“I mean, you see it,” Cora said. “We trust the guy in the seventh inning of games. What he did [during Sunday's game vs. the Rays] was outstanding. He’s done that every time he goes out there. The stuff is a lot better. The slider is a lot better.

“He has a different look. You’ve got [Colten] Brewer and Barnes and [Brandon Workman], who are tall and use fastballs, cutters, breaking balls, and he’s more like east and west with the sliders, so it’s a different look for that. He’s in the mix.”