SCOTTSDALE, Ariz. — As a team captain and starting running back on his championship football team at Scranton High in Pennsylvania, Joe McCarthy couldn’t afford to be patient.

When his offensive line opened up a hole at the line of scrimmage, McCarthy had to lower his shoulders and burst through it quickly. He rarely hesitated, as the converted quarterback racked up 2,275 yards and 27 rushing touchdowns over two seasons as a tailback after passing for 1,606 yards earlier in his career.

As an outfielder on the baseball team, McCarthy was a standout for a different reason. The lefty hit .500 as a senior, but when he left the bat on his shoulder, he remained an effective hitter.

“Even in high school I would walk a lot and take a lot of pitches to the point where my friends would always joke around about me not swinging the bat,” McCarthy said. “Guys still joke around about that today.”

Since debuting in the University of Virginia lineup in 2013, McCarthy, 26, has played seven seasons of baseball. The difference between his average and on-base percentage has been greater than 100 points for seven consecutive years.

In other words, Joe McCarthy walks the walk.

“Even since I was little, I was always a real patient hitter,” McCarthy said. “Controlling the strike zone is something I put a lot of emphasis on.”

Since debuting in the minors in 2015, McCarthy has posted high batting averages and low ones, too. He’s been healthy for extended stretches and he’s watched seasons wrecked by injury. Through the ups and downs in a game filled with failure, the outfielder’s plate discipline has never slumped.

As a freshman at Virginia, he hit .336, but walked 54 times in 60 games, allowing him to reach base at a .469 clip. During a rough junior season, McCarthy hit just .196 in 33 games, but he drew 24 walks and posted an impressive .343 on-base percentage.

His draft stock slipped, but evaluators recognized his world-class eye at the plate and McCarthy was drafted in the fifth round by the Tampa Bay Rays.

Since 2015, the average major league walk rate has hovered between 7.6-8.5 percent. In each of McCarthy’s four full seasons in the minors, his walk rate has been in the double digits, topping out at 16.2 percent in a 127-game stint with the Rays’ Double-A affiliate in 2017.

A herniated disk in McCarthy’s lower back limited him to just 53 minor league games in 2018 and 41 games with the Rays’ Triple-A affiliate before the 2019 trade deadline. As Tampa Bay prepared for an offseason 40-man roster crunch, the Giants jumped at the chance to acquire him in a low-profile minor league deal that was nothing more than a footnote given the flurry of activity on July 31.

Despite the positives that come with being a tough out, evaluating McCarthy’s true talent level has proven to be quite difficult. Is he a modern Scott Hatteberg, one of the poster children of the Oakland A’s’ “Moneyball” teams? Or will major league pitchers have an easier time figuring McCarthy out?

To prove he’s closer to the former and not the latter, McCarthy arrived to camp in Scottsdale well ahead of most peers.

“I actually showed up a month early just making sure my back was going to be healthy and ready to go for the season,” McCarthy said.

More than halfway through camp, it’s still difficult to gauge McCarthy’s potential.

When the Giants cut 17 players on Friday, his name was not on the list of players ticketed to spend the rest of spring at minor league camp.

The organization gave 2015 first round draft choice Chris Shaw marching orders on what to improve upon, but in the age of endless information and analytics, manager Gabe Kapler said the Giants are still trying to figure out McCarthy’s exact strengths and weaknesses.

“Farhan and myself and others have always liked Joe McCarthy going back to his time in Tampa,” Kapler said. “I think we’ve seen quite a bit more of Chris Shaw than we have of Joe McCarthy, and I think we have a pretty good understanding of the areas that Chris can focus on, whereas with Joe I think we’re still learning him and I think we need to see him a little bit more.”

After sticking past the first cuts, McCarthy drew a walk and hit his first home run of the spring in the Giants’ tie against the Brewers on Friday in Maryvale. The performance was a glimpse of a healthy McCarthy at his best: A hitter who takes pitches he can’t drive and hammers offerings he can drop his barrel on.

In 14 Cactus League plate appearances, McCarthy is 4-for-11 with three walks.

Is there a path for the under-the-radar trade acquisition to make the Opening Day roster? With a crowded outfield competition and minor league options at the left-handed hitter’s disposal, it’s unlikely he’ll break camp with the Giants. But as the team cycles through players and shuttles prospects back and forth from Triple-A to the big leagues this season, McCarthy may finally make his big league debut.

Good things come to those who wait. As his plate appearances suggest, McCarthy understands that better than anyone.