Mark Teixeira’s body simply kept breaking down.

As recently as this spring training, he talked boldly about wanting to play five more years. But then he incurred injuries to his knee, neck and shin this season, each keeping him off the field, each pushing him toward the inevitable.

Teixeira is scheduled to hold a 3 p.m. press conference Friday and, a source confirmed, it is to announce his retirement at the end of the season.

Teixeira is in the final season of an eight-year, $180 million contract. He might be able to land some kind of make-good deal next season, but not with the Yankees, who are trying to turn over their roster and get younger and plan to go with Greg Bird at first base.

In his time as a Yankee, he has put down both family and business roots in the New York area and made it clear he does not want to leave. Combine that with the deteriorating state of his body and game, and the decision becomes clearer.

Teixeira, 36, had his best season with the Yankees in 2009, his first year with the club. He was part of a free-agent class with CC Sabathia and A.J. Burnett brought in to make the Yankees’ first year in the new stadium special, and he finished second in the MVP voting as the Yankees went on to win their 27th title.

This has been the worst of Teixeira’s 14 big league seasons. The switch-hitter has been limited to 77 games, and he is hitting .198 with 10 homers, 27 RBIs and a .627 OPS.

At present, he has 404 homers, a career .872 OPS and five Gold Gloves. He ranks fifth all-time among switch-hitters in home runs, trailing Mickey Mantle, Eddie Murray, Chipper Jones and Carlos Beltran.

Teixeira is a three-time All-Star. His latest selection came in 2015, when he was having an MVP-type season until fracturing the right shin in August and missing the final month of the season. He finished with 31 homers and 79 RBIs in 111 games. Teixeira hasn’t played in more than 123 games since 2011, and has been on the disabled list every season since 2013.

Additional reporting by George A. King III