CHICAGO - The Giants have a power-hitting outfield prospect, and he just moved a step closer to the majors.

The Giants have promoted Chris Shaw, a left-handed hitter, to Triple-A after he hit .301 with six homers and a .901 OPS in his second season with the Flying Squirrels.

Most impressive, the 23-year-old he has struck out just 26 times in 154 plate appearances, great discipline for a power guy.

"With his bat, you pay attention, and he's drawing attention," general manager Bobby Evans said. "It's time for his shot at the next test. When the challenge comes at the next level, we'll see."

The Giants selected Shaw with the 31st pick of the 2015 draft out of Boston College. Though drafted as a first baseman, he had played about 100 games in the outfield, mostly in right, in college. The Giants moved him from first base to left field earlier this season at Double-A Richmond, Va. He has played 18 games there.

Giants fans are longing for the type of outfield power bat the organization hopes that Shaw possesses, but he is less likely to reach the majors after a few weeks of Triple-A as Christian Arroyo did, for two reasons.

First, the Giants want Shaw to get a little more professional experience in the outfield. Also, they do not need to put him on the 40-man roster until after the 2018 season, so they want to make sure he is ready not only to play in the majors, but to stay there.

While the Giants do not want to rush Shaw, they could not hold him back either.

"It was starting to get to the point where he needed a new challenge," Evans said. "We'd like to get him as much time as possible in Tripe-A to get comfortable."

In fact, Stanford alum Austin Slater is ahead of Shaw on the potential callup list. Besides Slater's numbers in his second Triple-A season (.313 average, .811 OPS), the Giants must put Slater on the 40-man after this season. That gives the Giants one fewer reason to hold him back.

Under different circumstances, Slater might have been called up already, but the Giants'' roster situation is complex.

They need to make room soon for three injured players - Aaron Hill, Conor Gillaspie an Hunter Pence. Hill and Gillaspie are expected back in the first or second game of a homestand that begins Friday, Pence more likely toward the end of the homestand or start of the next trip in Philadelphia. Pence will have to play some minor-league games first.

Denard Span's health also complicates matters. It forces the Giants to maintain depth in center field. They were looking at promoting Orlando Calixte, the former Royals minor-leaguer, because is on the 40-man roster and can play all three outfield positions and the infield. But Calixte was detoured by a concussion caused by crashing into a wall (a rather common malady in this organization this year) and just came off Sacramento's concussion list.

The Giants have been playing Kelby Tomlinson in center, but not necessarily to rush him up to the majors.

"We'd like to get him more time," Evans said.

Gorkys Hernandez has not been a good answer, offensively or defensively. If Calixte shows no ill effects of the concussion as he resumes play for Sacramento, it would not be a surprise to see him replace Hernandez.

The Giants' needs in the outfield are evident. They have a center and right fielder in their 30s, both beset by injuries, and have not been able to get much production from left field. Even with a 10-game hit streak for new left fielder Eduardo Nuñez, the Giants' outfield ranks last in the National League, by a large margin, with a .591 OPS.

Moving Shaw from first base to left field was not a snap decision, because they knew first base was blocked with Brandon Belt and Buster Posey.

"We discussed that this spring," Evans said. "We made more of a conscious decision to get him there primarily last month. It was discussed from the time we drafted him."

Meanwhile, some more changes at Sacramento: With the Giants close to selling Chris Marrero's rights to the Orix Blue Wave in Japan, Ryder Jones, Jae-Gyun Hwang and even Slater will get time at first base

Span returns: Span will be back in center field and leading off after missing two games with a thumb sprain. He faces Kyle Hendricks, while the Giants have Matt Moore in his first start against the Cubs since his eight-inning, two-run outing in Game 4 of the Division Series.

Span was questionable until he arrived for early treatment, took some swings in the cage and said he was good to go.

Your lineups:

GIANTS (vs. RHP Kyle Hendricks)

Span CF

Panik 2B

Belt 1B

Posey C

Crawford SS

Nuñez LF

Arroyo 3B

Williamson RF

Moore P

CUBS (vs. LHP Matt Moore)

Baez 2B

Almora Jr. CF

Bryant 3B

Rizzo 1B

Happ LF

Heyward RF

Russell SS

Montero C

Hendricks P

Henry Schulman is a San Francisco Chronicle staff writer. Email: hschulman@sfchronicle.com Twitter: @hankschulman