Seven missed tackles before halftime and none after.

The Broncos didn’t suddenly remember how to tackle in their season-opening win over Seattle. Likely, brain and body needed to be retrained after not playing for two weeks and not playing a full game since last year.

“Whatever you can call it — jitters, the excitement of the first game, wanting to make a big hit,” safety Justin Simmons said after practice Wednesday. “All that stuff combined definitely adds up. But that’s getting fixed in practice. You just have to be mentally aware of it.”

Simmons correctly pointed out he missed two tackles. He was one of three missed tackles (linebacker Bradley Chubb and safety Darian Stewart) on Seattle tight end Will Dissly’s 66-yard catch.

In the second half, the Broncos played with better fundamentals.

“Absolutely, we got better as the game went on,” inside linebacker Todd Davis said. “We do drills every day and it’s something that’s very important. We’ll keep getting better at it.”

The Broncos’ tackling plan needs to be good Sunday against Oakland because running back Marshawn Lynch still has the ability to carry defenders up the field.

“That’s how he’s been running his whole career: Downhill, always lowering his shoulders, keeping his feet moving on contact,” nose tackle Domata Peko said. “I’ve played him a couple times before and a key is swarming him. You can’t have one guy try and tackle him. Eleven hats on the football and knock that pile back.”

Henderson returns. Practice squad receiver Carlos Henderson went through his first practice after serving a suspension last week for violating the league’s policy on illegal substances.

“It felt good to be out there,” Henderson said. “I have to get my wind back and get back in shape, but most of all, I want to help the team get better.”

Coach Vance Joseph said last week Henderson’s main goal should center on becoming a better pro.

“I agree with him,” said Henderson, a 2017 third-round draft pick. “That’s what I’m doing, becoming a better pro off the field and handling my business and doing all of the right things.”

Welcome back. Safety Shamarko Thomas, released after the preseason but re-signed Tuesday, spent last week visiting his family on the East Coast.

“We had a good conversation with the coaches (on cut-down day) so I had a little bit of an idea,” Thomas said of re-joining the Broncos.

Thomas, who is one of five safeties on the active roster, said the Broncos’ “playbook is still in my head,” from the preseason.

“It’s just the altitude,” he said with a laugh. “It’s crazy because it took me a couple of days when I signed (in August) and then I leave for a week and I have to start over. But I’ll be good in two days.”

All players healthy. All 53 Broncos participated in Wednesday’s non-padded practice.

“Our team is in great condition,” Joseph said. “It was a warm day (Sunday) and guys played fast while they were tired. Obviously, some of it is luck (but) how we practice hopefully helps that.”

Footnotes. Sunday’s referee will be John Hussey, whose crew last week called a combined 26 penalties for 236 yards in Philadelphia’s opening-night win over Atlanta. It was the only game in which both teams had at least 100 yards in penalties. The Raiders, meanwhile, had 11 penalties for a league-high 155 yards in Monday’s loss to the Los Angeles Rams. … The Broncos signed receiver Isaiah McKenzie to fill out their practice squad. McKenzie has cleared waivers twice in the last week. … Defensive lineman Kyle Peko, released from the practice squad Monday, signed with Buffalo’s practice team.