Paxton has posted five shutout frames in two starts. He allowed just two hits with no walks and a strikeout on Wednesday, building again on his outstanding September as a late-season callup in 2013.
Going 3-0 with a 1.50 ERA in four starts down the stretch against the playoff-contending Rays, Cardinals, Tigers and Royals did wonders for the 25-year-old's outlook coming into this spring.
"It's a lot different," Paxton said. "Having that opportunity to go in September and do what I did really helped build my confidence. Having the success I did really showed me I belonged and can compete at that level."
Facing largely a second-unit Indians lineup, Paxton gave up a first-inning single to Ryan Raburn and a leadoff double in the second to Matt Carson, but otherwise kept Cleveland off balance. Eight of his nine outs never left the infield, including groundouts by the last five batters he faced.
"I just continued working on fastball command and moving in and out," Paxton said. "I threw some more curveballs today. They were feeling good. The first inning I left a few up, but I got on top of some and was feeling good. I was working on the changeup today and threw a few of those I was happy with. And the cutter, I left one up in the first inning, then threw a few others that felt pretty good. So my stuff is coming along."
With Iwakuma out, the only sure thing in the Mariners rotation is Felix Hernandez. Veteran non-roster invitees Scott Baker and Randy Wolf are competing for spots, along with youngsters Paxton, Erasmo Ramirez, Blake Beavan and Brandon Maurer.
This spring, Seattle's starters have allowed just two runs in 18 2/3 innings for a 0.96 ERA in eight games, though nobody is throwing more than three innings so far as they build up arm strength.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.