If heavy suddenly lies the crown on the defending Super Bowl champion Seahawks, it’s because slippery was the ball Sunday against the San Francisco 49ers.

Two lost fumbles and an interception thrown by Sam Darnold — one of his two on the day — resulted in three 49ers touchdowns and were the primary reason for San Francisco skipping out of town with a 32-29 win in an early battle for NFC West supremacy.

The 49ers, who got some revenge for two losses late last season against the Seahawks, including a 41-6 defeat in the divisional playoff game, are now 5-0 and have a two-game lead on the Seahawks in the West, as well as a head start on winning the head-to-head tiebreaker.

It was the second time in three games that Seahawks turnovers were the main reason for a loss, the other coming two weeks ago when three giveaways led to a 33-31 defeat at Washington. 

“We have to stay out of our own way at the end of the day,” Seahawks receiver Jaxon Smith-Njigba said. “We spotted them 21 points.”

The three turnovers that led to points all came in the first half — an interception thrown by Darnold at the Seattle 18, a fumble by running back Emanuel Wilson at the Seattle 11 and a fumble by George Holani in the end zone with 13 seconds left in the first half as the Seahawks were attempting to run out the clock. 

The latter was the most stunning, giving the 49ers a 21-13 halftime lead. The Seahawks had used their time outs on the previous drive hoping to get the ball and score before the half. They ended up with the ball at their own 4 following a 49ers punt. But San Francisco had all of its timeouts, so the Seahawks couldn’t just easily kneel out the half without potentially giving the ball back to the 49ers.

“We should be able to execute run plays,” Seahawks coach Mike Macdonald said. “We want to stay aggressive and get points at the end of the half, (with) the opportunity to get the ball coming out of the second half (Seattle was set to get the second-half kickoff). But we’ve got to be able to execute our run game and hold onto the football, straight up.”

Said Holani: “Definitely was a critical mistake. Just got to be able to be better with ball security, especially when we’re backed up like that. So that was a critical mistake. Got to be better.”

Even the usually sure-handed Smith-Njigba wasn’t immune, unable to control a Darnold pass with just under a minute left in the game and the Seahawks down three on a third-and-10 play from midfield that would have taken the ball inside San Francisco’s 20, if not closer. 

“That’s the one I want,” said Smith-Njigba, who caught five passes for 102 yards, including one for 35 yards three plays earlier to get the Seahawks to midfield. “So definitely would have loved to have those back. But I can’t sulk in it. … I guess I was thinking too much at that time. Just needed to play free and catch the ball at the end of the day.”

A play later, Cooper Kupp caught a Darnold pass at the Seattle sideline about a yard shy of the first down marker and tried to reach for the needed yards as he went out of bounds.

Kupp was ruled just short, with the call upheld after a review.

“I knew it was close,” Kupp said. “Clearly, it was short. Just not enough there, and we got to find a way to get that fourth down.”

NFL vice president of instant replay Mark Butterworth said: “A key thing to remember is we are looking at when the ball breaks from green, the field of play, to white, out of bounds. There was nothing clear and obvious to overturn the call on the field.”

When that ruling was finalized, the 49ers were able to celebrate a win in a game in which they were held 2 yards under their average per play this season — 4.8 compared to a 6.8 mark that led the NFL coming into the game — and in which they lost three turnovers of their own.

The Seahawks were held to a season-low 251 yards and averaged 3.4 per rush, their second lowest of the season.

A touchdown on a 24-yard drive following a muffed San Francisco punt forced by Nehemiah Pritchett allowed the Seahawks to tie the score at 7 in the first quarter and they appeared as if they’d go into the locker room at halftime down by just one before the Holani fumble.

“Without a doubt, there’s frustration,” Kupp said of the feeling at halftime. “We were very aware of how good the defense is playing. And then you gift them seven points there at the end. We just can’t do that. Offensively, we put the defense in a lot of really tough positions.”

Darnold threw his second pick of the game on the second play of the second half and the game felt as if it might be lost right there. But tough defense forced a 49ers field goal that was missed and the game turned.

A touchdown following a Pritchett interception in the third quarter and a field goal on the next possession following a fumble forced by Drake Thomas gave the Seahawks a 26-21 lead into the fourth quarter. 

The 49ers, who had just 159 yards in the first three quarters, finally got their offense going, mostly by finding ways to get the ball to veteran receiver Mike Evans, especially in matchups when covered by Josh Jobe.

Early in the fourth quarter, an Evans 23-yard reception against Jobe allowed the 49ers to convert a third-and-10, and a 28-yarder got them out of a second-and-21 hole. That led to a Brock Purdy TD pass to Brandin Cooks and a two-point pass to Evans — who had 113 yards on seven receptions — and a 29-26 lead with 11:02 left.

“Great individual plays by him,” Macdonald said.

Said 49ers coach Kyle Shanahan: “They do a really good job with their coverages, when to take people away and stuff. But every time they didn’t, it felt like Brock found it and Mike rewarded him for it.’’  

The Seahawks responded with a drive for a field goal by Jason Myers — his fifth of the game — to tie it at 29 with 6:55 left. 

The 49ers mostly used their running game — gains of 8, 13 and 11 — to get into position for an Eddy Pineiro field goal to go ahead 32-29 with 1:56 left. That Byron Murphy II and Uchenna Nwosu had combined to stop San Francisco’s Kaelon Black for a 1-yard loss on third-and-one forced the field goal and gave the Seahawks one more shot.

The ball slipped through Smith-Njigba’s hands, and with it the game and the NFC West lead.

The Seahawks were 3-2 at this point a year ago after a home loss to Tampa Bay and went 14-1 the rest of the way.

Seahawks players said they are confident this team can pull a similar rebound, one that will have to start quickly with a game Thursday night at Denver.

“I think our guys played hard,” Macdonald said. “We stuck together. I think we got a tough team. I think we’re a connected team. But in terms of playing complementary football the way that we want to play here as Seahawks and become the team that we want to become, we’re not there yet.“

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