SAN FRANCISCO >> When Blake Snell takes the hill tonight for the first time with the Giants, fans will understandably expect a cool-as-a-cucumber, kind of goofy, laid-back lefty, a guy who throws hard but games harder.

That may be the public persona that has become associated with the two-time Cy Young winner, aided by his devoted streaming audience on Twitch, his comic book-inspired nickname — “Snellzilla” — and endearing postgame soundbites through a drawl heard inside high school food courts up and down the West Coast.

When it comes time to lock in, though, such as 6:45 p.m. Monday evening, the Giants are learning there is a different side to their $62 million free-agent prize.

“I knew he was a funny dude and kind of goofy in some ways,” assistant pitching coach J.P. Martinez said. “But he’s an assassin when it comes to how to get ready for his pen work, how to go through his mound work.”

Snell began breaking down stereotypes as soon as he arrived in Scottsdale, signing his contract with only a week left in camp. Kyle Harrison, who idolized the fellow southpaw as a rising star at De La Salle, remembers the first conversation he had with him.

“I was like, ‘Kind of a goofball, dude?’ and he was like, ‘Nah man, I just love baseball and I love being around the team,’ “ Harrison recalled. “That’s what he’s been all about. He’s been nothing but that. That label does tend to stick around him, but I don’t know why. He’s a hard-ass worker. He works his butt off. He’s going to be great this year. I’m looking forward to watching him.”

As soon as the ink had dried on Snell’s contract, he was in uniform in the Giants’ dugout at Scottsdale Stadium. Before even being officially introduced — that would come the following morning — Snell sought out Martinez and pulled him aside for a 15-20 minute rundown in the dugout during the game that night.

“Just the amount of detail he went into about his pregame prep, his in-between start routine, he was just really dialed in,” Martinez said. “That made a really strong first impression on me, for sure. He’s just been so fun to watch work.”

The 23-year-old Harrison, in particular, has appreciated having another left-hander around to pick the mind of. He is scheduled to get the ball Tuesday, pairing the two southpaws back-to-back in the Giants’ rotation.

“He’s definitely a different kind of cat. But it’s a good cat to have,” Harrison said. “He talks like we’re different pitchers, the lefties. It’s kind of cool to see someone through that lens as well. He’s reserved, but not afraid to make fun of you. Not in a mean way. It’s always kind of in a caring way.”