Richard Perry/The New York Times

The Yankees’ frustrating off-season took another discouraging turn with the news Thursday that Andy Pettitte would retire. Pettitte called Hal Steinbrenner, the team’s managing general partner, to tell him his plans. The Yankees confirmed in a news release that Pettitte would make a formal announcement on Friday at 10:30 a.m. at Yankee Stadium.

The Yankees had hoped that Pettitte, 38, would continue pitching, and they were prepared to pay him $12 million or more to come back. But after missing two months last summer with a groin injury, Pettitte has decided to end his 16-year career.

After failing to sign the free-agent Cliff Lee, the Yankees badly wanted Pettitte back to solidify a rotation that is shaky beyond C. C. Sabathia, Phil Hughes and the erratic A. J. Burnett. Pettitte was an All-Star last season, when he was 11-3 with a 3.28 earned run average, and like Mike Mussina in 2008, he retires near the top of his game.

Pettitte is married with four children and lives in Deer Park, Tex. But he often said his family enjoyed spending summers in Westchester County, and Manager Joe Girardi recently said that Pettitte had been throwing this off-season.

But General Manager Brian Cashman has been doubtful all along. Cashman said Pettitte had told him not to count on him for 2011, and he proceeded under that assumption.

“At this stage, he’s decided not to pitch,” Cashman said last week, adding: “He’s a special guy. I think the bottom line is that people don’t want to let him go. And for good reason because he can still participate and be a championship-caliber pitcher, and no one wants to let him go.”

Even without counting on Pettitte — and with Lee having chosen to play for Philadelphia — Cashman has been measured in his efforts to upgrade the Yankees’ rotation. The team will open spring training in less than two weeks relying on Sergio Mitre, the rookie Ivan Nova and a collection of veterans with past health problems — Freddy Garcia, Bartolo Colon, Mark Prior — to comprise the back of its rotation.

Had Pettitte chosen to return, his season would have included a major distraction because of the Roger Clemens perjury trial, scheduled for July in Washington. Prosecutors plan to call Pettitte as a witness against Clemens, who has denied using performance-enhancing drugs. Pettitte has acknowledged using human growth hormone to help recover from an elbow injury in 2002.

Pettitte’s admission may complicate his chances at the Hall of Fame and his career earned run average, 3.88, would be the highest in Cooperstown. But Pettitte, who never played for a team with a losing record, is one of only eight pitchers with 240 victories and a .635 winning percentage. The others are Christy Mathewson, Grover Cleveland Alexander, Lefty Grove, Jim Palmer, Randy Johnson, Clemens and Mussina.

Pettitte retires with a career record of 240-138, and his 203 victories as a Yankee rank third on the team’s career list, behind the Hall of Famers Whitey Ford and Red Ruffing. He trails only Ford in strikeouts as a Yankee, with 1,823, and also ranks second in starts, with 396.

Pettitte’s postseason performance essentially mirrored his regular-season play. He was 19-10 with a 3.83 E.R.A. and is the career leader in postseason victories, including one for the Houston Astros, his team from 2004 through 2006. He won the clinching game of the World Series for the Yankees in 1998 and again in 2009.

Pettitte was also a pivotal member of the Yankees’ rotation in their championship seasons of 1996, 1999 and 2000. His retirement leaves Derek Jeter, Jorge Posada and Mariano Rivera as the only remaining Yankees who played for all five of the recent championship teams. Another homegrown Yankee, Bernie Williams, earned four rings in a career that ended in 2006.