Paxton has been outstanding when healthy over the past two years for Seattle, posting a 9-4 record and 2.66 ERA in 17 starts. But he missed much of last season with a strained lat muscle behind his left shoulder.
"We saw how dominant he could be last year," McClendon said. "We need him healthy. He's vital to our success."
The 26-year-old Canadian could be Seattle's No. 2 or 3 starter behind Felix Hernandez, depending on whether McClendon wants to break up Hernandez and fellow right-hander Hisashi Iwakuma in the rotation. But Paxton needs to be ready to roll by the start of the season in two weeks, and Sunday's outing was a big step in that direction.
"It was awesome," Paxton said of finally being back in game action. "It felt really good to get back out there with the guys behind me and be in the stadium again, get that feeling. It was a lot of fun."
It wasn't all smooth, however. Paxton got in early hot water when Elvis Andrus and Mitch Moreland laced one-out singles in the first to put runners at the corners, but he wiggled out of that with a double-play grounder by Kyle Blanks.
Paxton then gave up leadoff singles in the second to Carlos Peguero and Joey Gallo, but again escaped with three straight flyouts. A leadoff walk in the third was erased when catcher Jesus Sucre threw out Leonys Martin trying to steal second.
Paxton's day ended in the fourth when he struck out Blanks, but then gave up a single back up the middle to Peguero that glanced off his glove and bounded past second base. McClendon immediately called for reliever David Rollins with Paxton having thrown 61 pitches.
"It was good to get in situations and make some pitches when I had to to get out of it," Paxton said. "Ideally I'd like to throw less pitches in 3 1/3, but I'll tighten things up in the bullpen the next few times, and get things ready for the season."
Paxton said he was opening up a little early on his curveball and spiked one changeup with a too-firm grip, but those are not surprising occurrences in a spring debut.
"I thought he was pretty good," McClendon said. "His secondary stuff is not as sharp as it needs to be, but that's to be expected. He'll go to five [innings] next time out and build off of that one. It was a good outing."