Trumbo said the back tightened up while he was taking swings in the cage prior to the game.
"It just kind of grabbed," he said after Seattle's 13-0 loss to the Astros. "But it's gotten progressively better as the day's gone on. It's still not great, but it's a lot better than it was a couple hours ago."
With a four-hour flight to San Francisco, it remains to be seen how Trumbo feels on Monday. He said it was the first time he's had any problem with his back since a similar lower-back issue in 2007.
"As soon as I get the muscles to relax, I should be fine," Trumbo said. "Hopefully, overnight it'll get better and I'll be able to contribute tomorrow."
Trumbo, acquired from the D-backs in a trade on June 3, has hit just .162 (6-for-37) with no extra-base hits since his arrival, but he was coming off a two-hit game in Saturday's 8-1 win. He was replaced in left field by Dustin Ackley.
Trumbo has hit .242 with nine home runs and 24 RBIs in 55 games on the season with the D-backs and Mariners. The 29-year-old was slated to make his first start in left field on Sunday, having previously started six games at designated hitter, two in right field and one at first base.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB, read his Mariners Musings blog, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.