NEW YORK (CBSNewYork) — Sonny Gray says in an article he penned for The Players Tribune that his arrival to the Yankees is bittersweet.

On one hand, he had to say goodbye to the Oakland A’s, the only organization he had played for as a professional, one in which he built many great relationships and had good memories.

On the other hand, he’s thrilled about being thrust into a pennant race, he said.

“The guys have been awesome since I arrived, and have welcomed me with open arms,” wrote Gray, who was acquired by New York in a trade Monday. “And I know, just from having played against them earlier in the season, that I’m joining what’s a really good team to begin with: with a deep and talented pitching staff, and a deadly lineup that has no breaks in it. This is a tough, tough group. So I’m just coming here to play my part.

Sonny Gray

Yankees pitcher Sonny Gray talks to the media on Aug. 1, 2017. (Photo by Jim McIsaac/Getty Images)

Gray, who makes his first start as a Yankee on Thursday night at Cleveland, has only competed in the postseason once before, as a rookie in 2013, an experience he mentioned about in the article. “That’s the kind of game that you dream about pitching, growing up as a kid,” he wrote.

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The Yankees head into Thursday’s game with a 57-49 record, one game behind the Red Sox for the AL East lead.

The 27-year-old right-hander had a message for Yankees fans: “I’m a competitor. I love to compete. And when I get on the mound, that’s what I’m going to do. I’m going to compete, and I’m going to come at guys. I’m going to challenge guys, straight-up — with my best stuff against their best stuff.”

In the article, Gray wrote about his 2½-year-old son, Gunnar, and how they play one-on-one baseball around the house. The rules are loose, Gray said, except for one: Everyone must wear a hat — and usually both teams wore A’s hats.

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Just after Gray was traded, his wife bought Gunnar a Yankees cap, and they broke the news to the toddler, who asked, “Why, Dad? Why we’re not playing for the A’s anymore?”

“The beauty of 2½-year-olds, though, is that they’re also very understanding,” Gray wrote. “And so I just told him, ‘Well, buddy … we’re going to play for the Yankees now. After that, he started doing this thing, where he would repeat the words out loud, over and over: The Yankees … the Yankees … the Yankees! I think that was him just sort of trying them on — all part of his advanced process. Thankfully, the process worked, and slowly but surely he came around. I can now report that Gunnar is fully onboard with the trade.”