When the NFL lockout ended, Chargers players reported for physicals and coach Norv Turner sprang a conditioning test on them.

Welcome back to the NFL, Ryan Mathews.

"I think he was caught off guard by the run we had," Turner said Monday, five days after the second-year running back struggled to keep pace with his fellow skill players.

Mathews said when camp opened that he'd often run on a beach during the 4½-month lockout. As the Chargers ran gassers at Chargers Park — across the field's width and back in 16 seconds or less 10 times, with 45 seconds between sprints — Mathews discovered his beach runs weren't paying off so well.

"He's going to get a great opportunity to get in the best condition of his life," Turner said.

Not one to back down from a challenge, Mathews ran sprints after practices last week, then pronounced himself extra fit. "I feel better than ever," he said. "I feel fast, I feel quick, I feel strong."

Mathews missed practices with a foot injury on Sunday and Monday, a momentary detour, at the end of a tough first week for San Diego's 2010 first-round draft pick.

"He's got a little bit of a sore toe," Turner said. "He's going to practice as soon as he's comfortable with it. It's normal training camp stuff."

Turner sees big things for Mathews this season, starting with the opener Sept. 11 against the Minnesota Vikings.

"I expect him to be outstanding," the coach said.

Mathews wasn't shabby in 2010, although he said he topped out at 80 percent in speed and stamina after a high-ankle sprain in the second game. Among the nine running backs drafted last year, he finished first in both yards rushing (678) and touchdowns (seven). His average of 4.3 yards per carry also led the draft class, 48 carries minimum.

"Those stats are nice, but those aren't things we care about," Turner said.

With veteran running back Darren Sproles having signed with the Saints, the Chargers are counting on Mathews to help offset his departure. He'll need to stay healthy, which will allow him to learn in practice how to protect quarterback Philip Rivers from blitzers — a Sproles speciality — and when and were to go on pass routes that are a big part of Turner's diverse offense.

"We want to get him at full speed, we want to get him where he can play, get him into the rhythm of the game — play no matter what the situation is," Turner said. "There were some things he wasn't ready to do because he didn't practice enough. He'll be a lot more ready to handle whatever situation comes up this year."

The Chargers invested heavily in Mathews, moving up 16 spots and drafting him 12th overall, because they saw him as a three-down back.

At 6-foot and 218 pounds, he showed the speed to beat elite NFL defenders to the outside. He slammed the ball up the middle, too. Raw as a pass-catcher early in the season, he looked more fluid by year's end.

But like most rookies, he wasn't reliable enough to stay on the field for the entire series. Part of it was losing three fumbles, tying him with Bills back C.J. Spiller, the former Clemson speedster taken ninth, for the most in his draft class. The ankle injury and an arm injury were the bigger culprits, according to Turner.

"I was disappointed that he didn't get a chance," Turner said. "We talked about him playing 600 of our 1,000 snaps and getting 200 to 300 carries. He only played about 300 snaps and his carries (were 148).

"It's amazing what he did with the number of carries he has. He showed he's got the ability to be a game-breaker."

At practice Thursday, after he broke through a hole between the guards and darted past the linebackers, Mathews circled back and sought out running backs coach Ollie Wilson.

"How's my pad level?" he asked.

Running lower, Mathews said, is high on his to-do list for better health and ball security this season.

"In college, I'd run high and just want to look where I'm going," he said of his days at California State University at Frenso. "You can't do that at this level when you're going through the line. You've got to be able to keep your pads low until you get out of your break. Then, you want to go."

Last year, Turner was most impressed by Mathews' "physicality" and "competitiveness." However, top honors among Chargers backs went to Mike Tolbert, a 5-foot-9, 243-pounder who led the team in rushing.

Powered by Tolbert and given a speed boost from Mathews, the rushing offense went from 31st in 2009 to 15th last season. Turner said he expects another hefty improvement in the charts, with an offensive line that's intact for the third straight season adding horsepower.

Tolbert likes how he and Mathews mesh.

"I'm the type that likes to pound the defense down, and then he'll beat them around the corner," said Tolbert, who went undrafted out of Coastal Carolina in 2008.

A fear of messing up, Tolbert said, is the biggest challenge for a rookie running back. He expects Mathews to cut loose more this season.

"This is a tough offense to pick up," he said. "There are so many things we have to know and learn. I'm still learning today. For the amount of time he's had in the offense, and the amount of work he's had, Ryan is doing a good job."

As Mathews chips away at his learning curve, the game is slowing down.

"Last year, I was back there thinking a lot," he said. "And when you're thinking, you're not playing football. You're thinking. When you're comfortable in the backfield and able to run naturally, and make your cuts naturally and make your reads naturally — it's a lot better than having to think."