Exposito, 26, is batting .218/.254/.273 in 16 games and 59 plate appearances with Norfolk. He's 1-for-15 throwing out runners attempting to steal.
The Orioles also transferred catcher Luis Martinez from Double-A Bowie to Norfolk.
The Orioles' game notes say Monday's starter "is expected to be LH Zach Britton."
Britton is 0-0 with a 2.57 ERA in two career starts against the Mariners, both at Camden Yards. He threw nine scoreless innings in his first start against them on May 12, 2011, but Jason Vargas also threw nine scoreless in that game, a 2-1 Orioles win in 12 innings.
Today's starter, Miguel Gonzalez, has never faced the Athletics or anyone on their current 25-man roster.
Chris Davis is 3-for-7 with a home run against Bartolo Colon. J.J. Hardy is 2-for-17.
An Orioles victory today would clinch their first season series win against the A's since 1998. It also would even the all-time series at 249-249.
The Orioles have won four straight in Oakland, dating back to Sept. 16, 2012, for the first time since May 23-Sept. 9, 1998. A win today would give the Orioles five straight victories in Oakland for the first time since May 13-Aug. 16, 1996.
A win today would give the Orioles their first sweep of a four-game series in Oakland since May 22-25, 1987.
The Birds have recorded three consecutive quality starts in Oakland (Jason Hammel, Wei-Yin Chen and Chris Tillman) for the first time since April 16-18, 2010 (Kevin Millwood, Jeremy Guthrie and Brian Matusz). The last time the Orioles recorded four consecutive quality starts in Oakland was Aug. 15, 2005-Sept. 1, 2006 (Rodrigo Lopez, Bruce Chen, Eric DuBose and Erik Bedard).
Nate McLouth has reached base safely in 18 of his last 31 plate appearances. Over his last eight games, he's batting .458 (11-for-24) with seven walks and nine runs scored.
In the leadoff spot, McLouth is batting .333 (21-for-63) with 12 walks.
The Orioles have won a franchise-record 103 consecutive regular season games when leading after seven innings.