The Mariners are expected to call up McCaughan from Triple-A Tacoma prior to Wednesday's game against the Cubs, Ryan Divish of The Seattle Times reports.
The Mariners need fresh arms after Tuesday's 14-9 loss to the Cubs, and McCaughan will provide the club a multi-inning reliever while he's with the team. Jose Rodriguez threw three innings and likely won't be available for the next couple of games, so it seems likely he'll be the arm moved down to Tacoma in the corresponding transaction.