By Chad Finn, Boston.com Columnist

John Ryder has been named host of WEEI's pregame and postgame Red Sox coverage. The station also announced Wednesday that Lou Merloni and Sean Grande will periodically fill in for play-by-play announcer Dave O'Brien.

They replace Jon Rish, who resigned as host and fill-in broadcaster April 8 after choosing not to accept a pay cut.

Ryder, a Lakeville native who has been with WEEI since 1998, is a regular contributor to the evening "Planet Mikey" show. He also hosts "Red Sox Review" and "Celtics Rewind" after the teams' game broadcasts.

“John has done a stellar job in every role we’ve had for him and has absolutely earned this promotion,” said Jason Wolfe, vice president of programming for Entercom Boston. “He’s hosted the pre- and postgame shows for the Sox many times before and was a natural choice for us to fill this important job."

Grande, the radio voice of the Celtics since 2001, and Merloni, a former Red Sox infielder and current midday cohost on WEEI, will take turns stepping in for O'Brien on Monday nights. O'Brien is the play-by-play voice of ESPN's "Monday Night Baseball'' television broadcasts.

"Sean’s play-by-play experience speaks for itself,'' said Wolfe. "He’s one of the greats in the industry right now, and Lou’s expertise is second to none. There’s no baseball man in Boston who knows the Sox better than Lou."