Giants: Rough season prompts tough decisions.

Thursday was picture day for the Giants. The players, coaching staff, medical department and clubhouse personnel marched to left field at 4:45 p.m. for the annual team picture.

Anyone who forced a smile could be excused. Smiles, laughter and jollity have been rare this season, the positive vibes in Thursday night’s 11-2 thrashing of the A’s notwithstanding.

Terrible seasons prompt tough decisions, and manager Bruce Bochy has been forced into unfortunate conversations with players who have meant a lot to him and the organization.

It’s never easy to fire someone, especially a man whose home run in last year’s wildcard game catapulted the Giants into the next round of the playoffs, in which he also delivered some big hits.

Bochy told .163-hitting Conor Gillaspie after Wednesday night’s game he was designated for assignment, and the manager was taking the demotion hard Thursday. Still.

“This is the tough thing about going through a year like this,” Bochy said. “It goes with the territory, the changes. … It stinks.”

Another third baseman, Jae-Gyun Hwang, was optioned to Triple-A Sacramento, opening the door for Ryder Jones, who got promoted Thursday, started at third base, batted second and singled in his first two at-bats.

Another player added to the roster, outfielder Jarrett Parker, played his first big-league game since breaking his clavicle April 15 and doubled twice and singled. Jones and Parker went a combined 5-for-9, surpassing the number of hits (four) they had in 42 at-bats entering the game.

Brandon Belt and pitcher Ty Blach hit home runs, Blach’s a three-run shot to center field to complement his solid eight innings on the mound. It was just the Giants’ fourth threerun homer of the season and first at home.

The rout didn’t detract from the big picture, which is that the Giants own the majors’ secondworst record and need a transformation.

Bochy also told Denard Span he’ll be transitioning to left field, but the transition might not happen until spring training, if Span remains with the Giants. He has struggled mightily defensively — though he looked spry chasing down flies Thursday — and the team wants to find someone younger and quicker to play center.

“It’s hard to do during the season,” said Bochy, noting that Angel Pagan in 2016 needed all of spring training to feel comfortable when moving from center to left. “It’s a pretty good adjustment. It’s a different look in left field.”

Span’s and Pence’s contracts run through 2018, and it’s doubtful either will be relied on as much as they were this year. Bochy said he won’t start the same three outfielders every game, though Span and Pence were in the lineup again Thursday.

The only outfield change was Parker.

“This is a performance-related thing,” Bochy said. “Hopefully, he swings the bat well and forces the issue.”

He did, but it doesn’t mean he’ll get consistent at-bats. The Giants face lefties in two of three games in the upcoming Arizona series, and it’s a decent bet Parker won’t be in the lineup those days.

“It’s good to be a part of it again,” he said. “I’ve never had an injury this significant before, so I never missed a significant portion of the season. It’s difficult. It was great to be able to be back on the field and help out.”

Jones will get a long look at third, and it’s conceivable he and Christian Arroyo, who’s shelved with a wrist injury, will compete for playing time in spring training.

“He’ll get a chance here on a consistent basis to show what he can do,” Bochy said of Jones. “This is a perfect time for him.”

Jones felt far better than his first go-round with the Giants when he went 1-for-21, saying, “Obviously, I’m a little more comfortable. I’m starting to feel a little more comfortable out there, especially at the plate, trying to take deep breaths and have good at-bats.

“After the first two at-bats, I felt like, ‘Man, why did I make it so hard?’ ” Jones said. “That’s how baseball is. I hit some baseballs like that (during the first stint), and they were caught.”

So far, so good for Parker and Jones. Their arrival brought some energy and generated some smiles, not just because it was picture day.

John Shea is The San Francisco Chronicle’s national baseball writer. Email: jshea@ sfchronicle.com Twitter: @JohnSheaHey