PHOENIX — What does a manager say when he has to cut an experienced player after one at-bat five days after he first put on your uniform?

“Just be honest,” Bruce Bochy said. “You tell him we’re in a position where we have to activate a pitcher for a game tomorrow and it affects” him.

The player who heard that message late Saturday night was outfielder Aaron Altherr, who was designated for assignment eight days after the Giants claimed him on waivers from the Phillies to open a 25-man roster spot for Drew Pomeranz, who came off the injured list to start Sunday’s game.

Altherr got one at-bat, Friday night, and struck out looking.

Altherr was the seventh Giants player to be designated since Opening Day, partly a reflection of the front office overestimating the players’ abilities to hit in the majors but mostly a consequence of lacking players who have minor-league options.

“He’ll go through the process and we’ll see what happens,” Bochy said. “It’s a little bit of a tough deal because we couldn’t get him some at-bats. ... He’s been through this before.”

If Altherr clears waivers, the Giants can outright him to Triple-A Sacramento.

Sunday’s move gives the Giants a 40-man roster spot they can fill by claiming another player (Keon Broxton, anyone?) or promoting a nonroster player from Sacramento.

Now that they seem to have enough right-handed-hitting outfielders, they might want to give Mike Yastrzemski a tryout. The 28-year-old has hit 12 homers in 117 at-bats. But the grandson of Hall of Famer Carl Yastrzemski is playing in the hitter-friendly Pacific Coast League and has close to 3,000 minor-league plate appearances over six-plus seasons without a big-league call-up.

Suarez coming: The Giants will have to take yet another player off the 25-man roster Monday to make room for left-hander Andrew Suarez, who will be recalled from Sacramento to start the first of four games against Atlanta at Oracle Park.

Suarez made 29 starts as a rookie last year but did not make the team out of spring training. On April 21, he landed on the Triple-A injured list with a hamstring injury and allowed seven runs over 8 ⅔ innings in two games upon his return.

“Sure, he’s kicking off some rust,” Bochy said. “But a change like this, especially for a guy who’s made as many starts as he has, can be pretty uplifting and fire him up.”

Shaun Anderson makes his second big-league start Tuesday night.

Henry Schulman is a San Francisco Chronicle staff writer.