One Yankee started the 2018 MLB All-Star Game: outfielder Aaron Judge. He was selected to start for the American League and batted sixth while playing left field in the game at Nationals Park in Washington, D.C.
Judge was one of baseball's biggest stars in 2018. The previous season, he had won American League Rookie of the Year and set the then-rookie record with 52 home runs. In the 2018 All-Star Game, he showed that power again by hitting a home run in the second inning against Max Scherzer.
The American League starting lineup also included Mookie Betts, Mike Trout, José Altuve, José Ramírez, Manny Machado, José Abreu, and Salvador Pérez. Judge was the only player representing the Yankees in the starting lineup. Other Yankees could have been selected to the roster or entered later, but the question asks specifically about starters. The American League won the 10-inning game 8–6, with Alex Bregman named the Most Valuable Player.