SEATTLE – Mac Williamson’s cross-country journey on Wednesday ended in perfect fashion, with a trip around the bases on a three-run homer at T-Mobile Park in his first at-bat with the Mariners in Seattle’s 14-1 win over the Astros.

If you’re among those wondering “Who is this guy?” don’t feel bad. Mariners manager Scott Servais had never even met Williamson before the 28-year-old arrived shortly before game time after signing a Minor League contract with Seattle earlier in the day and then being quickly promoted to the big league club when it was discovered that Braden Bishop had a lacerated spleen.

The 6-foot-4, 237-pound outfielder has put up big Triple-A numbers, but he hit just .207 with 14 homers in 135 previous Major League games with the Giants over parts of five seasons and was designated for assignment two weeks ago.

After declining a Minor League assignment with San Francisco, he became a free agent and hadn't played in nearly two weeks while spending time at home with his family in North Carolina. But the Mariners called and he flew across the country, initially reporting to Triple-A Tacoma before he found out after one round of batting practice that he was needed in Seattle.

“It’s been a whirlwind,” Williamson said. “That was a long travel day, but it was well worth it.”

Even he was surprised when he unloaded a 403-foot blast to dead center off reliever Brady Rodgers in the five-run eighth.

“Considering I struck out eight of my last nine at-bats at San Francisco and I got down 1-2 there, I looked around and said, ‘You know what, I just need to put a ball in play in the outfield and a sac fly gets us a run,’” Williamson said. “When you get into the box and that competitive mentality, where it’s me vs. you, the adrenaline gets flowing and you just get in fight mode."

But a home run in his first at-bat in a stadium he'd never played in with a team he'd just shaken hands with in the dugout?

“I definitely didn’t expect that," he said. "I was hoping to make a positive impact early. That’s a good thing to do. That was fun.”