The Giants made several roster moves on Friday, but their decisions about the taxi squad for their final road trip before the Minor League season begins were equally intriguing.

Included among the five players working out with the club this weekend in San Diego are catcher Joey Bart and pitching prospect Kervin Castro. Though they aren’t on the active roster as members of the taxi squad, manager Gabe Kapler said their presence at Petco Park is anything but a formality.

“It looks like a small thing, but it’s something we don’t consider to be a small thing,” Kapler said.

Veteran catchers Buster Posey and Curt Casali had helped guide the Giants’ pitchers to a 2.93 team ERA entering Friday, second best in the Major Leagues. Whatever reps Bart loses by not playing camp games will be offset by the knowledge he gains with a few extra days around the veteran backstops.

“Joey’s here to spend time with Posey and Casali, plain and simple,” Kapler said. “The main goal … is to get Joey some exposure to the pregame work that Casali and Posey are doing.”

Bart, San Francisco's No. 2 prospect per MLB Pipeline, figures to join Triple-A Sacramento for the start of its season Thursday. The 24-year-old got 33 games of big league experience in 2020, when Posey elected not to play.

As for Castro, his inclusion on the taxi squad could be a precursor to a callup, a chance for exposure to the environment before he steps on a Major League mound. The 22-year-old right-hander is the organization’s No. 25 prospect and has not pitched above the short-season Class A level.

“I’m glad to have him with us on the taxi squad and kind of introduce him to Major League Baseball this way,” Kapler said. “Not sure if we’re going to have an opportunity to activate him anytime soon, but it’s good for him to get his feet wet.”

Roster shuffle
Outfielder Steven Duggar was called up from the alternate training site and started in center field against San Diego right-hander Yu Darvish on Friday. Infielder Jason Vosler (2-for-8 in four games) was optioned, while outfielder Skye Bolt (0-for-1 in two games) was designated for assignment.

Right-hander Zack Littell was called up and added to the 40-man roster. Right-handed relief pitching has been one blemish on the Giants’ otherwise sparkling 16-9 start.

Littell posted a 2.68 ERA in 29 games with the Twins in 2019, but he had a rough campaign last year for Minnesota, recording a 9.95 ERA in six games and spending two stints on the injured list (right elbow inflammation, left hamstring strain). Since joining the Giants’ organization, he has worked to develop a splitter and has raised his four-seam fastball velocity to 97 mph, Kapler said, an improvement of 3-4 mph.

“He had a nice camp for us, and he’s continued the strong work in his time at the alternate site,” Kapler said.

COVID protocols update
Kapler said the Giants are 13 days from exceeding the 85% vaccination threshold that would allow them to relax certain COVID-19 protocols. He said a group vaccinated on Thursday will push the club past the threshold.

Clubs were informed just before Opening Day that MLB and the MLBPA have agreed to relax certain health and safety protocols contained in the 2021 Operations Manual for fully vaccinated Tier 1 Individuals and for clubs where 85% of their Tier 1 Individuals are fully vaccinated. This applies to all players and staff who are considered Tier 1, including those at the alternate site. As part of that memo, players and staff were again strongly encouraged to receive one of the approved COVID-19 vaccines when eligible.

Worth noting
• Right-hander Johnny Cueto, who is on the IL with a lat strain, will throw a bullpen session Saturday.

“Things are moving in the right direction,” Kapler said.

• Right-hander Kevin Gausman (groin issue) had a strong bullpen session Friday and is set to start Sunday in San Diego, Kapler said. Gausman will be pitching on seven days’ rest.

• Vosler, infielder Thairo Estrada and left-hander Conner Menez joined Bart and Castro on the taxi squad.