Chargers keep injured receiver Mike Williams on the 53-man roster

There was a time this offseason when the Chargers were worried that their first-round draft pick, wide receiver Mike Williams, would be cut — by a surgeon.

Season-ending back surgery could have kept the team from seeing their prized rookie in their first season in Los Angeles, but a hope persisted that he’d be able to work his way back on the field.

When the Chargers went through their roster Saturday, doing cutting of their own, they decided that Williams, who missed all but the first day of training camp because of a back injury, had shown them enough to keep him on their 53-man roster.

The decision was one of a handful of moderate surprises made by general manager Tom Telesco and the organization that included jettisoning starting safety Dwight Lowery, incumbent kicker Josh Lambo and quarterback Kellen Clemens.

Tight end Jeff Cumberland, cornerback Trovon Reed, defensive end Caraun Reid and linebacker Joshua Perry, the team’s fourth-round pick last year, were also left off the roster.

After trimming from 90 to 53 players, the Chargers now have until late Sunday morning to make waiver claims before they fill out their 10-man practice squad, meaning players who survived the bubble today could be without work tomorrow.

In the case of Clemens, the Chargers, according to a team source, plan on bringing back the veteran quarterback later this week — a move that probably means the team wants to try to sneak a young player through waivers so he can be added to the practice squad.

Williams seemed like a logical candidate to begin the season on the physically unable to perform (PUP) list, which would havee kept him out the first six weeks of the regular season. But the Chargers’ rookie, who participated only in the first day of rookie minicamp before being sidelined with lower back problems, showed signs of improvement in recent weeks.

He has been running at full speed and, last week, began doing change-of-direction drills. By keeping him on the active roster, it appears there have been no setbacks. Chargers coach Anthony Lynn said Williams could play as soon as Week 4 against the Philadelphia Eagles.

By releasing Lowery, a nine-year veteran, the Chargers save $2 million and turn over the free safety duties to Tre Boston, whom the team signed after he was released by Carolina early in the offseason. Lowery started all 16 games for the Chargers last season.

The team also made a big switch on special teams with undrafted rookie Younghoe Koo beating out Lambo for the kicking job. The two players were nearly even throughout camp, with Koo maybe separating himself with his directional kicking on kickoffs.

Born in South Korea, Koo earned some fame in college after a video of him back-flipping after making a kick went viral.

He wasn’t the only undrafted player to earn a spot on the team. Running back Austin Ekeler, the breakout star of the team’s fourth preseason game, outlasted veteran Kenjon Barner and Andre Williams to win the No. 3 running back job.

Tight end Sean Culkin and linebackers Nigel Harris and James Onwualu also made the team, providing depth and athleticism on special teams. The team also elected to keep linebacker Denzel Perryman on the active roster despite undergoing ankle surgery during training camp. While he’s starting the season on the active roster, the plan is for Perryman to start the season on the injured reserve with the hope he’ll be able to return.

Undrafted cornerback and former Glendale High star Michael Davis, who received a lot of reps during the preseason, didn’t make the team but could be a candidate for the practice squad.

Each of the Chargers’ draft picks, with the exception of second-round pick Forrest Lamp, who is on the injured reserve, made the initial 53-man roster.

The Chargers open the season Sept. 11 in Denver.

dan.woike@latimes.com

Twitter: @DanWoikeSports