FLOWERY BRANCH, Ga. — When the Atlanta Falcons drafted Jake Matthews, they figured he would take over at left tackle someday. They didn’t expect it to be this soon.

Midway through his first NFL preseason, the Falcons shifted Matthews across the line Monday to replace Sam Baker, who went down with a season-ending knee injury.

Matthews, the No. 6 overall pick, was expected to break into the league at right tackle, a less-demanding position than protecting quarterback Matt Ryan’s blind side. Now the rookie will have to step up to the challenge right away.

“I think the coaches are going to put me in good situations,” Matthews said. “If I keep getting reps, I’ll be ready to go.”

Baker suffered a torn patellar tendon in his right knee during a 32-7 loss to Houston in a preseason game Saturday, hindering Atlanta’s plans for revamping the offensive line.

The team struggled up front last season, a big reason the Falcons ranked last in the league in rushing and gave up 44 sacks, the most in Ryan’s career.

The Falcons used their top draft pick on Matthews and signed free agent Jon Asamoah, another instant starter at right guard. Baker, a former first-round pick who played only four games last season because of a knee injury, also was part of the rebuilding effort.

Coach Mike Smith tried to put the best face on Baker going down again.

“As soon as we had confirmation that Sam wasn’t going to be able to play anymore this season, it’s an easy switch,” he said. “Jake is a No. 1 pick, the sixth pick in the draft, he’s got left tackle written all over him.”

Former starter Lamar Holmes, who had been Baker’s backup, moved over to take Matthews’ spot on the right side. Gabe Carimi and Ryan Schraeder will compete for playing time as well, though Carimi is banged up at the moment.

Chiefs

CHARLES WAS HURT MOVING OUT OF DORM: Jamaal Charles made it through every tackle from the Chiefs’ defense during three weeks at Missouri Western. It wasn’t until he was leaving training camp that he got hurt.

Charles was in the process of moving out of the dorms Thursday, when the team was getting ready to shift the rest of camp to their own practice facility, when he came to a grassy slope. He wound up slipping a bit and turned his foot.

X-rays and MRI exams ensued, and Charles did not make the trip to Carolina for Sunday’s preseason game. And while all the tests came back negative, coach Andy Reid said he’s unsure just how long the explosive running back will be out.

“He’s feeling better. We’re optimistic about it,” Reid said.

Reid did not say whether Charles will be available Saturday against Green Bay.

Cardinals

DOCKETT TEARS ACL, OUT FOR SEASON: Arizona defensive tackle Darnell Dockett, one of the most durable players in the NFL in the past decade, tore the ACL in his right knee in practice and will have season-ending surgery.

The team said the extent of the injury was revealed in an MRI on Monday. The 6-foot-4, 290-pound Dockett has missed only two games in 10 NFL seasons. He has started 156 of the 158 in which he appeared.

Dockett was hurt in an 11-on-11 drill. He limped away but had to be helped onto a cart. Dockett lay on his back as he was carted off the field.

Monday’s game

REDSKINS 24, BROWNS 23: In Washington, Johnny Manziel struggled to hit open receivers and added another gesture to his repertoire — a middle finger apparently aimed at the opponents’ bench — in the Browns’ loss to the Redskins.

Neither Manziel nor Brian Hoyer did much to claim the starting QB job.

Manziel, the No. 22 pick in the draft, was 7-of-16 passes for 65 yards and a touchdown. Hoyer was 2-for-6 for 16 yards. Both players’ stats were padded by series against the Redskins’ backups.

Coach Mike Pettine has said he plans to announce his regular-season starter Tuesday.

Around the league

Tight end Rob Gronkowski participated in contact drills with the Patriots for the first time since knee surgery in January. ... Bills rookie receiver Sammy Watkins is day to day after tests confirmed a diagnosis of bruised ribs, a person close to the situation said. ... Raiders rookie quarterback Derek Carr returned to practice three days after being knocked out of a game with a concussion and sore ribs.