Ravens coach John Harbaugh has a simple theory on the use of challenge flags: The best way to maintain a winning percentage is to keep that red flag tucked into your belt line.

“But I don’t think that way,” he said.

Since 2008, Harbaugh has challenged 129 calls. He’s gotten 54 successfully overturned, compared with 75 upheld. That’s the most losses on a challenge among active NFL coaches, eking out Andy Reid’s 72 losses on 143 attempts. Bill Belichick, the third winningest NFL coach ever, lost 78 out of 131.

Harbaugh reached for his challenge flag twice during Sunday’s 26-23 loss to the Las Vegas Raiders. And twice, he was unsuccessful, costing the Ravens a pair of timeouts and momentum as they dropped to 0-2 for the first time since 2015. Harbaugh has lost six consecutive challenges, with his last successful challenge coming on Jan. 1, 2023, according to Pro Football Reference.

“I’m not worried about the record,” Harbaugh said Monday afternoon. “I’m trying to think about the opportunity in the game to see if we have a chance to use a challenge to our advantage and try to win the game.”

His first challenge came in the second quarter on a low throw to Zay Flowers against the left sideline. Rules analyst Gene Steratore called it a “pretty clean short hop” on the CBS broadcast but microphones near the field picked up Flowers repeating, “That’s a catch!”

“That’s probably a situation where I don’t mind taking a chance there on that one because Zay did have his hand under the ball,” Harbaugh said. “Maybe there’s a chance they’ll turn that over. I thought it was probably less than 50-50 when I saw it.

“I looked at it. I saw it. I knew what happened right away. I thought, you know what? I don’t mind the timeout right here, let me see if we can get them to turn that one over.”

Lamar Jackson threw an incomplete pass on the next play. Then Justin Tucker sailed a 56-yard field goal try wide left and the Ravens failed to turn a three-point game into a two-possession contest heading into the final two minutes of the first half.

Harbaugh’s second challenge was more costly. He threw the flag to review an impressive Davante Adams’ toe drag along the sideline, a play that Harbaugh said “was moving fast.”

“I saw it from afar and I saw it quickly on the replay board,” Harbaugh said. “It was a quick shot in the replay booth. I thought to myself, ‘It’s really close. There’s a good chance his toes are still on the ground but there’s a chance his toes are off the ground.’ And we didn’t have enough time to get another look at it.”

He made a split-second decision to go for it behind the thinking that if they could get it overturned it would have helped close out a win. And if it didn’t get overturned, he hoped the lost timeout wouldn’t be a difference-maker.

Las Vegas kicker Daniel Carlson connected from 25 yards four plays later to trim Baltimore’s lead to 23-16 in the fourth quarter. Because of the lost challenge, the Ravens didn’t have a timeout when they got the ball back with 27 seconds and a final chance at saving their fourth-quarter collapse.

Harbaugh’s philosophy of whether to challenge a call extends beyond simply not caring about his record. In a situation like that where Adams’ catch required a flash decision, he’ll normally — and he pressed a fist to his chest as he said this — only throw it when he’s sure.

“I decided on that one to take a shot,” Harbaugh said, “and it hurt us because we didn’t have the timeout at the end of the game.”