KIRKLAND, Wash. — The first defeat for the Seattle Seahawks as defending Super Bowl champions was not accepted easily.

Seattle players found it tough to take being on the losing end in San Diego Sunday with the Chargers winning 30-21 — a game played in a mid-90s heat and 33 percent humidity.

Their frustration was probably best demonstrated by running back Marshawn Lynch, the engine that literally made the Seahawks run last season when he rushed for 1,257 yards, ratifying the style of play he called “Beast Mode.” Lynch carried only six times for 36 yards and left the field with about a minute left in the game.

But the Seahawks didn’t have long to wallow in any misery with the team they defeated in the Super Bowl — Denver — set to come to Seattle Sunday afternoon.

“They are quiet and serious,” coach Pete Carroll said of the mood of his team on Monday. “We don’t take these easily, you know. These are very high expectations that we live with here and everybody knows that.

“And the main thing is that everybody took to heart the changes and the adjustments and the things that we can fix. And they are ready to do that. I think we came out of here together on what we felt happened.”

What happened was Seattle’s defense surprisingly could not get off the field against the Chargers, who ran 75 plays and held the ball for almost 43 minutes behind precision passing from quarterback Philip Rivers.

Rivers mostly executed the team’s trademark dink-and-dunk offense to get the Chargers in scoring range.

Once there, he was able to hit tight end Antonio Gates on three touchdown passes that proved the difference.

“They were able to get themselves in real manageable third down situations,” Carroll said. “They were moving it like crazy and they just kept the ball away from us.” San Diego was 10-17 on third downs, five of which needed two yards or less to convert.

Some sloppy Seattle play also proved pivotal. A fumble by Percy Harvin on a kickoff return led to a San Diego touchdown and a 20-7 lead late in the second quarter. Seattle also had eight penalties and about as many missed tackles on defense and blocks on offense.

“It wasn’t anything we did not prepare for,” said safety Earl Thomas. “We just did not execute when it really mattered. Sometimes, games are just funny and strange. It was hot out there. We were out there for a long time and there was a lot of cramping up. We just have to fight through the situation.

“This was a great learning experience; Chargers had a great game plan. They were ready for what we were throwing at them. We didn’t execute like we normally do.”

Still, Seattle had the ball down 27-21 with 3:04 remaining, with Carroll thinking the Seahawks would find a way to win. Instead, Seattle went four and out and the game was over; the Chargers later adding a field goal for the final margin.

That Seattle’s offense was on the field for just 40 plays meant Lynch’s (six carries) and Harvin’s (three touches) numbers were unacceptable, Carroll said.

Lynch departed for the locker room with just over a minute left in the game and Seattle down 27-21. But Carroll said Lynch was not frustrated. Rather, Carroll said Lynch had a tight back and was merely heading to the locker room early to deal with the injury.

Carroll said it is something the team has to constantly monitor.

Seattle is 1-1 and fell behind 2-0 Arizona in the NFC West, the first time since the end of the 2012 season it has not been in first place in the division.

“We played a really tough football game and a tough team that was ready and we were up against a team that played really, really good ball and we needed to make some plays when the opportunities were there for us and we didn’t get that done,” Carroll said Monday. “What it really came down to was their ability to control the football. They were able to control the game by doing that and get a great win.”

Seattle had three players leave the game due to cramps — safeties Earl Thomas and Kam Chancellor and cornerback Byron Maxwell. All returned. But their departures for a few plays were indicative of the toll the heat took on the Seahawks.

Seattle had not lost by more than a touchdown since a 23-13 loss at Dallas on Nov. 6, 2011.

REPORT CARD VS. CHARGERS

–PASSING OFFENSE: B — It was fine early, as Russell Wilson was 4-for-5 for 62 yards in the first quarter, which ended with Seattle ahead, 7-3. But then San Diego’s offense took control of the game and the Seahawks simply did not have enough chances to get into an offensive rhythm. Once Seattle was behind and forced to play catch-up, Wilson was under constant pressure as the Seahawks made more than the usual number of assignment errors up front, allowing the Chargers to come free at times. Rookie right tackle Justin Britt had a particularly tough time. Wilson also wasn’t quite as sharp at the end as needed.

–RUSHING OFFENSE: B — Seattle had just 13 rushing attempts, fewer than any game last year when the low was 15 against the Rams. Seattle ran it well enough when it had the chance with Marshawn Lynch getting 36 yards on six carries. But simply not having the ball enough meant for something of a lost day all around on offense.

–PASS DEFENSE: C-minus — The “Legion of Boom” was uncharacteristically giving against the Chargers, allowing 276 yards and three touchdowns. The heat was undoubtedly a factor — all three of the Seattle players who left with cramps were in the secondary and safety Kam Chancellor said he was bothered almost the entire game. Chancellor was beaten for one touchdown by San Diego tight end Antonio Gates, for whom Seattle’s defense never had an answer. Seattle also tried all of its linebackers on Gates, but none had any real success on a rare day when Seattle was passed over early and often. Even Richard Sherman gave up three completions, and while none were long, it was indicative of a tough day for the Seahawks.

–RUSH DEFENSE: B — The stats indicate that Seattle played the run pretty well as the Chargers had 101 yards on 37 carries, just 2.7 per attempt. But the stats are a little misleading as the Chargers picked up some key gains on the ground, including a few by Rivers, who finished with 17 yards on 11 attempts. Missed tackles were also again an issue, as they were in the first game.

–SPECIAL TEAMS: C — One big mistakes was enough to drag down the special teams grade — a fumble on a kickoff return by Percy Harvin that gave the Chargers the ball at the Seattle 28 and led to a touchdown that put San Diego ahead 20-7 late in the second quarter. Seattle never got closer than six the rest of the way. The coverage units were fine and Seattle didn’t hurt itself in the rest of the kicking game. But nothing was spectacular.

–COACHING: C — Seattle’s first loss since Dec. 22, 2013, was a hard one to read. Seattle seemed to have a good game plan on offense early, with a new wrinkle in the zone read leading to a 51-yard touchdown run by Harvin. And the defensive game plan early also figured to be good enough to give Seattle a chance to win. But then the heat seemed to take over and the Seahawks made a number of mistakes. Maybe blame the Seahawks for not making a better adjustment to the San Diego offense in the second half, and for not figuring out how to get Harvin the ball more than three times on offense.