Michael Morse is on his way from the Nationals to the Mariners. (AP)

The Nationals agreed to a three-way deal that will send first baseman/outfielder Michael Morse to the Mariners. The Mariners will send first baseman/catcher John Jaso to the Athletics, with Oakland sending right-hander A.J. Cole, right-hander Blake Treinen and a player to be named back to the Nationals, the organization that drafted and signed Cole before dealing the hard-throwing prospect to the A’s last year in the Gio Gonzalez deal.

The Red Sox, according to a major league source, had some interest in Morse, a 30-year-old with prodigious power. Over the last three years in Washington, Morse hit .296/.345/.516/.861 while averaging 21 homers a season (30 homers per 162 games), including a .291/.321/.470/.791 line with 18 homers in 102 games in 2012.

However, according to the source, the Sox felt that the cost of acquisition for Morse — who will be under team control for just one year (for $6.75 million) before he is eligible for free agency following the 2013 season — was “steep” given the market alternatives (including, of course, free agent Mike Napoli, with whom the Sox continue to talk about the possibility of a deal).

Given that the Nationals received a pitcher with the upside of a potential frontline starter in Cole (albeit one who struggled in the High-A California League, resulting in a demotion to the Single-A Midwest League, where he dominated (2.07 ERA, 102 strikeouts, 19 walks in 96 innings)), a comparable prospect price from the Sox might have been someone along the lines of one of the Sox’ top tier of pitching prospects, perhaps a high-ceiling pitcher far from the majors such as Henry Owens, but more likely, a pitcher like Matt Barnes, Rubby De La Rosa or Allen Webster.