Ten Major League umpires, including seven crew chiefs, are set to retire, according to sources.

It marks the largest turnover at the job since 1999.

Some of the retirements are due to nagging injuries while others are coincidental, as a group of the umpires entered the league around the same time.

Crew chiefs Ted Barrett, Greg Gibson, Tom Hallion, Sam Holbrook, Jerry Meals, Jim Reynolds and Bill Welke are among the retirements, while Marty Foster, Paul Nauert and Tim Timmons will join them.

The retirements have nothing to do with upcoming on-the-field rule changes for 2023, nor the possibility of the automatic balls and strikes system being instituted at the MLB level in the near future.