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6/22/2014 2:18 A.M. ET

Back tightness prompts Morse's early exit

PHOENIX -- Giants first baseman Michael Morse left the game in the fifth inning against the D-backs on Saturday night with back tightness.

After striking out in the fourth inning, Morse was looked at by an athletic trainer. He played first base in the bottom of the fourth, but Joaquin Arias replaced him in the bottom of the fifth inning.

"Not too worried about it. Just treat it tomorrow," Morse said after the Giants' 6-4 victory.

Morse said he doesn't expect to be out long and may be back in the lineup for Monday's home game against the Padres.

Morse said his back has been bothering him since the Giants played the White Sox on Tuesday and Wednesday, and it tightened up while swinging Saturday.

"The balls were down and in, and I'm not really a down-and-in hitter," Morse said. "But I swung for them and felt a little tightness in my back."

Morse is hitting .286 with an .866 OPS (on-base plus slugging percentage). He was one of multiple players filling in at first base for the injured Brandon Belt, who has been out since May 9 with a broken left thumb.

Although Morse likely won't miss much time, the Giants are short on outfielders after sending Juan Perez to Triple-A Fresno before Saturday's game. The only outfielders who will likely be available for Sunday's game are Gregor Blanco, Tyler Colvin and Hunter Pence. Manager Bruce Bochy did not rule out making a roster move to bring in a healthy fourth outfielder.

"Obviously, Angel [Pagan] is in the conversation along with Morse," Bochy said. "If we need to make a move ... we'll continue that conversation."

Giants bring up infielder Panik from Triple-A

PHOENIX -- Joe Panik has arrived in the Giants clubhouse, but his glove has not.

The 23-year-old infielder was called up from Triple-A Fresno early Saturday morning, and he joined the Giants in Phoenix for their game against the D-backs, but most of his baseball equipment is in a connecting city.

"Makes for a good story," Panik said.

To make room for Panik, the Giants optioned outfielder Juan Perez to Fresno and designated pitcher Jake Dunning for assignment.

Panik, the 29th overall pick in the 2011 First-Year Player Draft, got the call that he would be joining the Giants at about 1:30 in the morning and quickly called his parents in New York.

"My dad answered the phone in his groggy voice, and Mom gets on speakerphone, 'What's wrong?'" Panik said. "'Well, this is actually probably the first good call you'll get at 3 a.m.'"

Panik said his parents, Natalie and Paul, flew into Phoenix for Saturday's game and actually beat him to the airport.

Panik was raking before the Giants called him up. At Fresno, he was hitting .321 in 74 games with a .829 OPS (on-base plus slugging percentage).

"This year, I felt like this offseason I prepared myself well physically," he said.

"I didn't try to press this year; I didn't try to do too much because I knew if I played my game, everything would work out."

Panik, whom MLB.com ranked as the Giants' No. 14 prospect, said manager Bruce Bochy hadn't discussed what his role with the team would be, but Bochy did say that Panik will likely make his first start against the D-backs on Sunday. Panik pinch-hit in the eighth inning Saturday and earned a walk.

"He's doing a real nice job," Bochy said. "This is a promotion he's earned. ... And we think at this point we could use some help at second base."

Belt takes BP, could start rehab stint soon

PHOENIX -- First baseman Brandon Belt has been on the disabled list since suffering a broken left thumb May 9, but he is making strides toward returning to the Giants.

Belt took batting practice Friday for the first time since the injury and is looking to start a rehab stint within the next 10 days.

"I'm not in charge of it, but I think the initial time frame would be I would do some rehab stuff a week to 10 days from now," Belt said. "I'm on schedule right now and I feel pretty good."

Belt said batting practice went well, and his thumb didn't bother him.

"The more I pushed it, the better it felt," he said.

Manager Bruce Bochy said Belt's performance in batting practice could result in an accelerated start to his rehab stint.

"He's further along than I thought, the way he was swinging," Bochy said. "There's a possibility we could ramp up his work and get his rehab started even earlier.

"You watch them, you see where they're at, how they're playing, their timing. We like to keep them down there till we think they're ready."

Giants hold off on Pagan resuming action

PHOENIX -- Outfielder Angel Pagan's return to the Giants' lineup was pushed back Saturday.

Before Friday's game, manager Bruce Bochy said Pagan might play Saturday, but the 32-year-old outfielder was out of the lineup for the fifth straight game before the Giants' matchup with the D-backs.

Although Pagan is sitting out another game, Bochy said the team would not place him on the disabled list.

"We're going to hold off. He's really close," Bochy said. "If we [placed him on the DL] then he's probably going to miss another nine games when he could be ready in a couple days."

Pagan has been out with lower back stiffness since Sunday. Gregor Blanco and Juan Perez have played in his place, but Saturday, the Giants sent Perez to Triple-A to make room for infielder Joe Panik, showing that the Giants believe Pagan will return soon.

Bochy said they might let Pagan take it easy during pregame warmups, where he took batting practice and fly balls Friday, because he would not play Saturday.

"We'll give him a day or two and see where we're at," Bochy said. "He's making progress."

Pagan currently leads the Giants in batting average (.307) and is the only player on the team with more than 10 stolen bases.

Since Pagan has been out of the lineup, Blanco has been the Giants' leadoff hitter and has gone 4-for-16.

Adam Lichtenstein is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.