From almost the moment the Giants picked him in the second round of the 2009 amateur draft, catcher Tommy Joseph became a poster boy for bad luck, as if he had crossed paths with a caravan of black cats while walking under a ladder.

How funny was it, then, that Joseph got the call for his major-league debut on Friday the 13th?

Joseph’s star no longer seems crossed. After four concussions, a wrist operation and a position change, the key player in the 2012 trade that brought Hunter Pence to San Francisco is two weeks into a major-league career with the most surprising team in baseball, poised to supplant three-time All-Star Ryan Howard as the Phillies’ everyday first baseman.

“It’s definitely been quite a ride for sure with everything that’s happened since I became a Phillie,” Joseph said by phone from Detroit on Tuesday, the day after he hit his second big-league home run.

“It’s all been worth it because I got the opportunity.”

If Joseph is still with the big club June 24, he will suit up against the Giants in the opener of a three-game series at AT&T Park. Perhaps he will share the field with Pence, who joined the Giants because the Phillies thought Joseph could be the heir to catcher Carlos Ruiz.

The frailty of the human brain ruined those plans.

Joseph already had two concussions while catching in the Giants’ system, in 2010 at low Class A Augusta from a foul tip and 2012 with Double-A Richmond when a batter inadvertently whacked his head on a backswing.

In 2013, already promoted to the Phillies’ Triple-A team in Lehigh Valley, Pa., another foul tip meant another concussion. The wrist surgery came in 2014, the fourth concussion in 2015.

That one ended his catching career, not merely because the Phillies feared for his long-term health, but it began to affect his vision, creating astigmatism.

“When we found out there were vision issues, obviously that was a scare to me because I didn’t see that coming at all,” Joseph said.

Joseph’s conversion to first base was easier than most. His offense had been ahead of his catching and projected well for a corner-infield spot, and he played some first base at Horizon High School in Scottsdale, Ariz.

The Giants’ philosophy on versatility also served Joseph well. They have all their minor-league catchers play some first base. Joseph had 40 games there before he was traded.

On Friday the 13th, almost a year after the permanent switch, Joseph was standing at first base at Citizens Bank Park, playing for a team that was supposed to “tank” in 2016 but has stunned the National League East with a 26-21 record.

“When I ran onto the field for the first time and threw the ball around the infield, then threw it to Mickey Morandini, our first-base coach, I took a second to look around and thought, ‘All right. I’m here. This is pretty cool,’” Joseph said.

He went 0-for-2 with a walk and a run in a 3-2 victory over the Reds. In nine games, including seven starts, Joseph is 8-for-27 ( .296) with a double, two homers and four RBIs.

“The team was playing very well before I got here,” Joseph said. “When I stepped in, I knew I had to hit the ground rolling and follow everybody’s lead here and contribute, and be part of the success story.”

Given all that Joseph has endured in more than six years as a professional, it’s easy to forget he is only 24. He still could have a long big-league career if he can hit and endures no long-term effects from four concussions.

“Right now, I’m definitely not worried about it,” he said. “I think that I was able to catch all the symptoms and all issues I was having at the early stages. The doctors I’ve worked with have been great.”

Pence has made his mark with the Giants since a trade that also sent Nate Schierholtz and pitcher Seth Rosin to Philly. Joseph can take pride in knowing he was dealt for a player who made a huge impact.

“I don’t think I’ve ever heard anybody say a negative thing about Hunter,” Joseph said. “To me, that’s cool being associated with somebody like that. Not only was it a great trade for the Giants, but he’s a role model and a leader in the clubhouse. Obviously, the two World Series are very important as well.”

Henry Schulman is a San Francisco Chronicle staff writer. Email: hschulman@sfchronicle.com Twitter: hankschulman