SAN FRANCISCO -- Less than a year after garnering National League Rookie of the Year consideration, Dereck Rodríguez is heading back to the Minors.

The Giants optioned the struggling right-hander to Triple-A Sacramento on Saturday following a string of three rough starts and activated catcher Erik Kratz off the 10-day injured list.

Rodriguez emerged as one of the breakout stars of the Giants’ 2018 campaign, posting a sparkling 2.81 ERA over 21 appearances, but he showed signs of regression over the first two months of this season, logging a 5.05 ERA over his first eight starts.

Rodriguez admitted that the news did not come as a complete surprise to him.

“Honestly, not really,” Rodriguez said. “Not really. The way things have been going this year. I had three pretty tough outings. It’s part of the game. I’m not the first or the last one it’s going to happen to. Now it’s just my job to go down there and keep my head high and just throw strikes. That’s what they want me to do, throw strikes and get back up here as soon as possible.”

Rodriguez, 26, has uncharacteristically battled command issues, issuing four walks in each of his last three starts and 17 over 41 innings this year. Rodriguez said he hopes going to Sacramento will allow him to refine his command in a lower-pressure environment.

“He’s going to go down to just try to polish some things up, get that good command that he had last year,” manager Bruce Bochy said. “He got in a little rut there. We all hit bumps in the road, and this is all this is for him. He’ll be back up here.”

Rodriguez was slated to make his next start during the Giants’ two-game series against the Blue Jays next week. The club has not announced who will replace him in the rotation. Tyler Beede, who is currently in the bullpen and already made one spot start for the Giants this year, is a strong candidate for the spot.

Altherr joins outfield mix
The Giants claimed Aaron Altherr off waivers from the Phillies on Saturday and cleared a spot for him on the 40-man roster by designating right-hander Andrew Moore for assignment.

Altherr is expected to join the Giants on Tuesday ahead of their series opener against the Blue Jays. The Phillies cut Altherr after his 1-for-29 start to the season, but the Giants still see upside in the 28-year-old outfielder, who is only two years removed crushing 19 home runs and posting an .856 OPS over 107 games. Altherr struggled to sustain that success with the Phillies last year, batting .181 with a .628 OPS.

“He’s a kid with some good skills, a high ceiling,” Bochy said. “If you go back to ‘17, that was a pretty good year for him. He’s had some struggles, but you like what’s in there.”

Altherr’s arrival isn’t expected to impact Mac Williamson’s standing with the club, as Bochy said Williamson will continue to get an extended look in left field. The Giants won’t need to make a corresponding move on the 25-man roster until Altherr is activated on Tuesday.

Injury updates
• Brandon Belt (right knee inflammation) was out of the lineup against the Reds on Saturday, but his MRI exam came back clean and he could return to action as soon as Sunday.

• Buster Posey (concussion) woke up feeling better on Saturday and appears to be “getting over the hump,” according to Bochy. He will be eligible to come off the seven-day concussion list on Wednesday.