But ESPN, the powerhouse sports network, may not lack an outlet in the Boston market for long. According to multiple industry sources, ESPN is in discussions to air some of its national programming on WEEI-AM 850 during nights and weekends, with WEEI intending to move to an FM station within months. (Entercom Communications, which owns WEEI, also owns two FM stations in Boston: WAAF 97.7/107.3, and Mike 93.7.)

ESPN Radio would then take over the 850 spot on the dial. The new ESPN 850 station would then be affiliated with the ESPN Boston website, which launches Monday.

This development adds to the recent frenzy in Boston sports radio competition, which became considerably more contentious in mid-August, when the CBS Radio-owned “98.5 The Sports Hub’’ launched on WBZ’s FM signal, issuing the first legitimate challenge to WEEI’s local dominance.

WAMG was expected to be that challenger upon its debut in July 2005. It hired former Boston Her ald sportswriter and WEEI contributor Michael Felger to host a drive-time program to go toe-to-toe with WEEI’s “The Big Show,’’ hosted by Glenn Ordway.

But WAMG had no play-by-play affiliations with local franchises, and its national programming struggled in a provincial sports market. In recent months, the station had aired just five hours of local programming daily.

What proved most damaging, WAMG’s signal strength didn’t extend much beyond Boston, and faded to static in the early evening. While a source who previously worked at the station said last night that it had made significant gains in advertising last summer, it failed to make a dent in the ratings. And its future looked even bleaker in July, when Felger left to return to WEEI and contribute to the station’s upstart website. He has since moved to “The Sports Hub,’’ where he hosts the drive-time program.

WAMG, which is owned by the investment firm WallerSutton, is expected to switch formats Monday, though one source at the station said employees were not told what the plan was and there is some belief that the signal will go dark.

Several WAMG staffers, among them on-air personalities Bob Lobel, Kevin Winter, and Chris Villani, were informed of the decision to end the all-sports format Thursday.