SAN DIEGO -- Left-hander Will Smith will reprise his role as the Giants' closer to start the season, manager Bruce Bochy announced Thursday ahead of the club's Opening Day matchup against the Padres at Petco Park.

"I'll be calling for Smitty," Bochy said. "I talked to the bullpen, and we're going to work it similar to how we worked it at the back end of last season. Smitty will ascend to the closing role."

Smith, 29, served as the Giants' closer for the second half of last year and logged a 2.55 ERA over 53 innings after returning from Tommy John surgery in May.

The bullpen figures to be a major strength for the Giants, who will also have Tony Watson, Sam Dyson, Reyes Moronta, Mark Melancon, Nick Vincent, Trevor Gott and Rule 5 Draft pick Travis Bergen in their relief corps. Bochy said the unit's depth will allow him to turn to a few other options on days when Smith is unavailable.

"It's a bullpen that has a lot of experience, as far as guys pitching late in the ballgame, closing games," Bochy said. "If you look at Smitty, Watson, Melancon, Dyson, Moronta, they're all capable of pitching the eighth and ninth. I told them that. We're just in a unique position here. If guys need a break, it could be Moronta closing one day."

President of baseball operations Farhan Zaidi had said throughout the offseason that the Giants were open to subtracting from their bullpen depth to fill other holes on their roster, particularly in the outfield, though no deals ultimately came to fruition.

"It was a really deep reliever market in free agency this offseason," Zaidi said. "We like our relievers, so they weren't just fodder for us to trade and acquire other pieces. A deal like that, certainly it made sense on paper, but we didn't line up on anything that we thought made sense for us."

Williamson DFA'd

The Giants had been hoping that Mac Williamson would enjoy a strong spring and force his way onto the club's roster, but it didn't end up working out that way. After batting .237 with a .608 OPS in 22 exhibition games, Williamson was designated for assignment Thursday, along with Alen Hanson and Tom Murphy.

"I know it's going to be disappointing for Mac," Bochy said. "We looked at the outfield situation and we just didn't have really anybody that stepped up at that time."

Williamson appeared poised for a breakout season last year before he tripped over the bullpen mounds and sustained a concussion that wrecked his year. He could remain in the Giants' organization if he clears waivers, but Zaidi said he hopes the 28-year-old can latch on with another team.

"For his sake and his career, I hope he gets an opportunity somewhere," Zaidi said.

The Giants opted to carry Steven Duggar, Gerardo Parra, Michael Reed and Rule 5 Draft pick Connor Joe as outfielders, with utility man Yangervis Solarte also available to provide coverage in left field. Joe and Reed, both of whom were acquired in the last week, started in the corner outfield spots for the Giants against Padres left-hander Eric Lauer in Thursday's 2-0 Opening Day loss.

"We've said all along that where we are as a franchise and organization, to have a successful season, we're going to need some contributions from guys that our fans aren't familiar with yet," Zaidi said. "It'll be up to them now to make the fans familiar with them with what they do on the field."

Joe, who made his MLB debut in his hometown of San Diego on Thursday, became the 13th different left fielder to start for the Giants on Opening Day in the last 13 years.

Worth noting

• Hanson's omission opened a spot on the bench for Pablo Sandoval, who also helped his cause down the stretch with a series of productive at-bats against left-handed pitching.

"I think he certainly benefited, not just from the way he played down the stretch, but his general versatility," Zaidi said.

The Giants' confidence in Abiatal Avelino also allowed them to cut ties with Hanson and leave Solarte as the backup shortstop. Avelino will start the season at Triple-A Sacramento, but he could be called up in the event of an injury to starter Brandon Crawford.

• Right-handers Jose Lopez and Merandy Gonzalez were claimed off waivers by the Reds and Cardinals, respectively. Left-hander Steven Okert cleared waivers and was outrighted to Triple-A Sacramento.