SEATTLE -- As they prepare for a tough 10-game stretch against the best teams in the American League East, the Mariners moved to beef up their bullpen on Thursday by promoting right-handers Nick Rumbelow and Rob Whalen from Triple-A Tacoma.
First baseman Daniel Vogelbach was optioned back to Tacoma and right-handed reliever Mike Morin was designated for assignment to open spots on the Major League roster. Both Rumbelow and Whalen will be available for Thursday's series opener against Boston at Safeco Field as Seattle embarks on a stretch where it plays two series against the Red Sox and one against the Yankees.
The moves bring the Mariners back to an eight-man bullpen and reinforce a group that currently has Juan Nicasio and Nick Vincent on the 10-day disabled list, though both could return next week on Seattle's upcoming road trip to New York and Boston.
Rumbelow, 26, will be making his Mariners debut and first return to the Majors since 2015, when he appeared in 17 games as a reliever for the Yankees. He was acquired from New York in November for Minor League pitchers JP Sears and Juan Then and figured in the Mariners' bullpen plans until being sidelined by a nerve issue in his neck during Spring Training.
Rumbelow has pitched three scoreless innings in three outings for Tacoma, allowing one hit and two walks with five strikeouts, and says he's back to full strength.
"I feel where I need to be," Rumbelow said. "I'm the guy they brought over, health-wise and everything else, 100 percent. It was beautiful to just be back out there competing. That's what I love to do out on the mound. Not having that for a little bit just continued to light that fire. Being down in Peoria and seeing the Mariners play so well, you want to be a part of that."
The Texas native missed almost all of 2016 following Tommy John surgery, then split last year between Double-A Trenton and Triple-A Scranton/Wilkes-Barre, going a combined 5-1 with six saves and a 1.12 ERA with 45 strikeouts in 40 1/3 innings.
"He's got good stuff," said Mariners manager Scott Servais. "A mid-90s fastball, very good changeup and hard breaking ball. It's legit stuff. He's only had a handful of outings in Triple-A, but everybody has been really excited about what they've seen from him so far."
Whalen has been starting for Tacoma, but the 24-year-old figures to provide a long relief option for Seattle for now. He's gone 7-3 with a 4.50 ERA in 13 starts for the Rainiers, including 4-1 with a 3.23 ERA over his last seven outings.
Whalen has pitched in seven Major League games over the previous two seasons, including two with the Mariners in 2017 after being acquired from the Braves. He was 0-1 with a 6.14 ERA in one start and one relief appearance for Seattle and left the Rainiers in midseason to deal with depression and anxiety issues.
But Whalen came back strong and impressed the Mariners this spring and has carried that on with a solid start in Tacoma. Servais said he adds length to the bullpen if needed, particularly with Roenis Elias having thrown two innings in Wednesday's 8-6 win over the Angels.
"I came in this spring with no expectations after last year and all the things that happened," Whalen said. "I just wanted to come in and have fun again and enjoy what I get to do for a living. With the help of my pitching coaches, things got off to a good start and I've just tried to keep it rolling."
With Ryon Healy performing well at first base, Vogelbach had been used sparingly in his latest stint with Seattle. He appeared in one game since being recalled on June 8, going 1-for-2 with a walk and RBI in a game at Tampa Bay. He's hit .210 with two home runs and six RBIs in 62 at-bats for the Mariners overall this year.

Morin also was recalled by the Mariners on June 8 and he made two relief appearances, allowing one run in two innings with three strikeouts and a walk. He's gone 2-1 with three saves and a 3.24 ERA in 20 outings with Tacoma this year.
Morin is out of Minor League options, so he was designated for assignment and could be kept in the organization if he clears waivers. That move puts the Mariners' 40-man roster now at 39.
Worth noting
• Third baseman Kyle Seager rejoined the team on Thursday after missing Wednesday's game to tend to a family issue.
"Everything seems to be okay there at home," Servais said. "He's good. His wife is pregnant and we just wanted to make sure things are where they need to be there. He's anxious to get back in there. I told him he missed a good game [Wednesday] and he said, 'Oh, I know. I was following it.'"
• Vincent threw on the flat ground again and did some running to test his strained right groin muscle. Nicasio also threw as he works back from a swollen right knee. Both could throw bullpen sessions this weekend and then be ready for rehab outings and quick returns to the big-league club.
• Catcher Chris Herrmann, on the 10-day DL with strained right oblique, started a rehab stint at Tacoma on Wednesday and went 0-for-3 and scored a run while playing designated hitter in a 5-3 win over Omaha.