Williams joins in after a long wait

Receiver makes NFL debut and contributes with a crucial catch in Chargers victory.

OAKLAND — It was a simple “dig” route, a play in which Mike Williams sprinted about 15 yards downfield and made a quick 90-degree turn toward the middle.

Chargers quarterback Philip Rivers, on third and six from the Oakland Raiders 34-yard line and his team trailing by three points in the fourth quarter, timed his pass so it would reach its target just as Williams came out of his break.

Williams, the former Clemson star who was the seventh overall pick in April’s draft, leaped for the ball and hauled it in for a 15yard gain, giving the Chargers a first down at the 19.

Five plays later, Rivers connected with Melvin Gordon on a six-yard pass that gave the Chargers a 14-10 lead in a game they went on to win 17-16.

“I just had to get my depth, get past the chains and make the catch,” Williams said. “I was just waiting for the opportunity, it came, and I made the best of it.”

It was a long wait. The 6foot-4, 220-pound Williams suffered a herniated disk in his lower back in early May. He sat out training camp and the first five games of the season, the Chargers choosing a conservative route with the rehabilitation of their prized draft pick.

Williams made his longawaited NFL debut Sunday but seemed to spend much of the afternoon in bubblewrap. He played only 10 snaps and Rivers barely looked his way until that fourth-quarter pass, Williams’ only target.

But it turned out to be a key catch of a touchdownscoring drive that helped push the Chargers to their second consecutive narrow victory.

“He came through when we needed him,” Gordon said. “He only had one catch, but it was one that helped get us into a position to win. That’s what he’s here for.”

Williams hadn’t played in a game since Jan. 9, when he helped Clemson beat Alabama for the national championship. He acknowledged having a few “jitters” before his first NFL game, which quickly dissipated after his first contact.

“I was looking to get that first hit, my welcome to the NFL,” Williams said. “That was good. Every time they called a pass play, I thought I’d have an opportunity to make my first NFL catch.”

Williams and the Chargers believe it will be the first of many.

“He got his feet wet today,” Gordon said. “Once he gets in stride, he’s just so big, he’s gonna be a possession receiver that I don’t think anyone is gonna be able to stop, especially over the top.”

Williams’ size, speed and strength could add a dimension to an already deep and diverse receiving corps that includes two standout tight ends in Hunter Henry and Antonio Gates, an outstanding possession receiver in Keenan Allen, and two breakaway threats in Travis Benjamin and Tyrell Williams.

“I think he does a great job of attacking the ball while it’s in the air,” Allen said. “He has great hands, and he’s huge. Any time you have a guy like that, somebody has to pay attention to him. If they don’t, he’ll just do what he does.”

Mike Williams didn’t enter Sunday’s game until there was a minute left in the first quarter. He played two snaps in the second quarter before expanding his role in the second half.

“We wanted to sprinkle him in some, let him ease his way in,” Rivers said. “We knew if he got zone coverage, he was going to have a chance to be the primary guy on the in route. He’s a big target. He did a nice job. He was excited about his first catch, getting action in a division game on the road.

“I know he’s been in huge crowds his whole career, national championship games, but I think that was good for him. Now we can continue to mix him in and keep Travis and Tyrell and all the guys fresh.”

mike.digiovanna@latimes.com Twitter: @MikeDiGiovanna