SEATTLE -- While the Mariners still haven’t announced a starter for Tuesday’s game in Texas since sending rookie right-hander Erik Swanson back to Triple-A Tacoma, manager Scott Servais said Saturday the replacement will not be top pitching prospect Justus Sheffield.

Seattle’s No. 1 ranked prospect by MLB Pipeline threw 5 2/3 innings on Friday night in a no-decision for Tacoma in Reno and wouldn’t be ready to make his next start until Wednesday.

Veteran southpaw Tommy Milone is lined up to pitch Tuesday for Tacoma and would appear a prime candidate to be promoted for at least a spot start, having gone 4-2 with a 3.83 ERA in nine outings (eight starts), or the Mariners could go with a bullpen day since they currently have nine relievers.

The 32-year-old Milone would need to be added to the 40-man roster since he initially signed with Seattle on a Minor League deal, but he’s an eight-year MLB veteran with a career mark of 46-37 with a 4.42 ERA in 151 games (131 starts) for five different teams since 2011.

Sheffield pitched a three-inning relief stint behind Yusei Kikuchi’s abbreviated start several weeks ago, but the Mariners aren’t looking to rush him back until he’s ready to stick. The 23-year-old is 1-2 with a 4.38 ERA in eight outings (seven starts) for Tacoma and gave up five hits and three runs with three walks and six strikeouts in his latest start in Reno.

“I think when we get to the point where we call Justus up, we’d like to call him up and leave him here and let him go,” Servais said. “I don’t want to call him up and give him one or two outings and then go back and forth. He’s working on things right now.”

Servais said recent reports on Sheffield have been good as he’s focusing more on his changeup and cautioned not to read too much into the numbers out of the Pacific Coast League.

“There’s a lot of positives there,” Servais said. “Sometimes getting caught up in the line score in the PCL right now is dangerous. We’re not at the games, so it’s all we can really look at. So you really have to go with the people who are there, giving us reports on the stuff, the command, the hits.

“If you look at the numbers in the PCL this year, they are off the chart. They’re playing with the Major League baseball in Triple-A this year and it’s changed the game quite a bit. I think it’s a good thing for the pitchers to not have to make an adjustment when they come to the big leagues with the ball, but the numbers are up dramatically.”

Mike Leake is slated to start Monday’s series opener in Arlington and Marco Gonzales is penciled in for Wednesday’s finale, but Swanson was sent down after giving up four homers in his last outing, putting the rookie at 1-5 with an 8.04 ERA in seven games (six starts) in Seattle.

Both Sheffield and Swanson were acquired from the Yankees in the James Paxton trade, along with outfielder Dom Thompson-Williams, who is performing very well in Double-A Arkansas.

Festa returns to Triple-A after impressing skipper

Rookie right-hander Matt Festa, who impressed Servais with his two-inning outing in Friday’s 7-1 loss to the Twins, was optioned back to Tacoma on Saturday to open a spot for starter Wade LeBlanc, who was activated off the injured list.

Festa, ranked by MLB Pipeline as the Mariners' No. 17 prospect, was recalled prior to Friday’s game to bolster Seattle's bullpen and pitched the final two innings, allowing two hits and one run with two strikeouts while throwing 20 strikes in a 28-pitch outing.

“I thought Matt Festa threw the ball really well,” Servais said. “That was probably the best outing I’ve ever seen Matt have. He’s added some things to his game. Those were a couple bright spots from guys who can really help our bullpen down the road.”

Injury updates

• Third baseman Kyle Seager (tendon surgery in left hand) has hit .308 (4-for-13) with a double, three runs and an RBI in his first three rehab games for Tacoma as he works toward a likely return next Saturday when he’s eligible to come off the 60-day disabled list.

• Utility man Dylan Moore reported to Tacoma on Saturday to begin his rehab stint as he recovers from a bruised right wrist. He could be ready to return as soon as Monday in Texas, though the Mariners now have veteran Tim Beckham also working in a utility role since promoting J.P. Crawford to play shortstop.

• Reliever Sam Tuivailala (right Achilles' tendon surgery) also reported to Tacoma to continue his rehab stint after allowing one run in six innings over six outings with Advanced-A Modesto.

Fellow right-hander Gerson Bautista (strained right pec) threw a perfect inning with two strikeouts in his second day of back-to-back outings for Modesto on Friday and will soon be promoted to Tacoma as well. He’s allowed two earned runs in five innings in five appearances.

• Servais said Felix Hernandez (strained right lat muscle) has begun doing rehab work, but yet to pick up a baseball since going on the 10-day IL earlier this week for what is expected to be a 4-6 week layoff.

“He’s working out and getting after it really good,” Servais said. “I know he wants to get back as quick as he can. The reports are good there. But he’s not throwing yet.”