As it turns out, the Bolts had been eyeing Bosa since last season -- when they assumed they had no shot at the best defensive player in the country.
Ricky Henne of the team's official website compiled a fascinating oral history of the Bosa pick, going back to scouting process of 2015.
"I was watching some film on him and I remember walking down the hall to (director of player personnel) JoJo (Wooden) and saying, 'Can you imagine if we can get a guy like this?'" president of football operations John Spanos said. "He made a comment to me that unless we were picking first overall, he didn't think that was going to happen. And I remember thinking he was probably right."
Coach Mike McCoy and general manager Tom Telesco were on the same page, pouring over Bosa's game film with jaw-dropping amazement.
After watching Bosa's performance in the January 1 Fiesta Bowl, Telesco walked away planning to select him at No. 3 if available.
"The text I got basically said 'we're going to get our guy,'" Spanos explained. "And I knew that meant a trade must have just come though. It wasn't until Philadelphia made that trade that I finally believed we'd have the chance to draft Joey."
The Chargers had two weeks to consider trade scenarios, which led to a wave of unfounded rumors seemingly connecting them to every consensus top prospect except Bosa. Telesco insists nobody even asked him about the Ohio State star, and he wasn't going to go out of his way to disclose his plans.
"It was amusing to see," Spanos said. "We would sit back, read these mock drafts and see who people thought we would take. We would look around at each other and say, 'Man, I can't believe no one knows.'"
Added McCoy, "You do laugh at it all because nobody has any idea what any team is doing besides those in each building. It's pure speculation. Everyone has an opinion. We knew the direction we were heading. We were happy to keep our thoughts for every player, not just the number three pick, close to the vest. So the mock drafts brought some smiles to our faces. We knew what we were doing. Our decision was easy. Once those trades went through and you knew the quarterbacks were going one and two, if we stayed at three, we knew we were taking Joey Bosa."
By the time draft night rolled around, the Bolts were ready to pull the trigger on the player who resided atop their draft board "for some time."
"I thought back to that conversation with JoJo, and how we thought there would be no way we could get him without the number one pick," Spanos said, putting a tidy bow on the story. "Now here we are five months later and he's a Charger. We were all just so excited."