Lester has struggled this season but has pitched well of late, winning three of his last four starts. He takes the mound Tuesday with a record of 8-11 and a 5.01 ERA.
For the Mariners, Beavan is coming off a win against the Minnesota Twins in which he went seven innings, allowing only five hits and two runs. The 23-year-old right-hander enters Tuesday's contest with a 9-8 record and with an ERA of 4.95.
Red Sox second baseman Dustin Pedroia was 2-for-3 with a run in Monday's game. He is in the midst of a 14-game hitting streak, tied for the longest streak of his 2012 season. David Ortiz remains out while he nurses an Achilles injury.