With Spring Training rapidly approaching, we're taking an in-depth look at the Mariners' roster. This is the ninth and final part of an Around the Horn series looking at each position on the team. Today: the bullpen.
The big question: Can the 'Wolfpack' make a difference?
General manager Jerry Dipoto has spoken at length about the growing trend in MLB toward shorter starts and fewer innings from the rotation, with versatile, hard-throwing relievers stepping up to fill the gap and control the end of games.
With that in mind, the Mariners made Juan Nicasio their primary free-agent acquisition of the offseason after acquiring David Phelps last July. Both are former starters who throw hard and are capable of multi-innings if needed.
With young closer Edwin Diaz and veteran setup man Nick Vincent also returning, the back of the bullpen looks very solid and Seattle has a nice group of young power arms coming up as well. Dipoto's plan is to build enough quality depth and versatility to give those relievers sufficient rest and recovery time so that the bullpen can stay fresh and keep attacking all year.

The six sure things: Diaz, Nicasio, Vincent, Phelps, Marc Rzepczynski, James Pazos
Along with the four right-handers, Rzepczynski and Pazos would seem like locks for the two lefty roles. Rzepczynski struggled at the end of last year, but is an established veteran who still has one year and $5.5 million remaining on the deal he signed last season. Pazos was one of the pleasant surprises last year as a rookie and the Mariners are very high on his potential.
Other contenders: Tony Zych, Dan Altavilla, Nick Rumbelow, Shawn Armstrong
The Mariners would like to go with an eight-man bullpen. If they can pull that off, they'll be able to carry at least two of these four on Opening Day and have others waiting in the wings as needed. Armstrong, acquired from the Indians, is the only one out of Minor League options, so that might give him an initial edge in landing a roster spot if he has a solid spring.

Rumbelow is another intriguing newcomer, acquired from the Yankees. He had an excellent Triple-A season last year after having Tommy John surgery in '16. Zych and Altavilla are hard-throwing right-handers with good upside and easily could crack the Opening Day roster if they stay healthy and post solid springs.
Depth: Chasen Bradford, Mike Morin, Ryan Garton, Casey Lawrence, Ryan Cook
Bradford and Morin were claimed off waivers this winter, Bradford after pitching 28 games for the Mets as a rookie and Morin from the Angels after spending most of the year in Triple-A. Bradford has Minor League options and could ride the Tacoma shuttle as an effective right-hander. Morin has more MLB experience with 183 games in four seasons, mostly with the Angels, but is out of options.
Garton pitched well as a September callup last year after being acquired from the Rays and returned on a Minor League deal. Lawrence is in the same boat after arriving midseason from Toronto. Cook is another non-roster invitee as a former All-Star with the A's in 2012 who signed with Seattle initially in '16 but was sidelined almost all of the past two years with arm problems. He will get another shot now at age 30.

If the Mariners are going to have a roster surprise or two this spring, it may well come out of this group.
In the pipeline
The Mariners have a couple intriguing relief prospects who emerged last year in Art Warren (their No. 15 prospect per MLB Pipeline) and Matthew Festa (No. 16), who are in camp for the first time as non-roster invitees. Rumbelow (No. 23) is the other Top 30 prospect among the relievers in camp.

Seth Elledge (No. 18), Wyatt Mills (No. 19) and Darin Gillies (No. 25) are relief prospects who'll report to Minor League camp later in the month.
By the numbers
Diaz had the fourth-most saves in the Majors last year with 34, and his 12.14 strikeouts per nine innings were the fourth best by a reliever in club history. But for some reason, the 23-year-old closer was far better on the road (1.24 ERA, opponents batting average of .106 with 25 saves in 27 chances) than at Safeco Field (5.76 ERA, .265 opponents BA with nine saves in 12 chances).