Determining closer next step for improved 'pen

The D-backs' bullpen experienced a huge turnaround in 2017, and the club is hoping for similar results with most of last year's cast of characters returning.
D-backs relievers compiled a 3.78 ERA in 2017, good for fifth in the Majors, after ranking 27th with a 4.94 ERA in '16.
One of the reasons for the bullpen's struggles in 2016 was the inability of Arizona's rotation to pitch deep into games. That forced the bullpen to throw 567 innings that year as opposed to just 499 2/3 in '17.
• Projected:Lineup | Rotation
MLB.com is taking a look at the projected bullpen of all 30 teams ahead of Spring Training. Here's how the D-backs might stack up:
BULLPEN IF SEASON STARTED TODAY
Archie Bradley, RHP (Closer)
Brad Boxberger, RHP
Yoshihisa Hirano, RHP
Andrew Chafin, LHP
Jimmy Sherfy, RHP
Randall Delgado, RHP
T.J. McFarland, LHP
STRENGTH
When they were putting together the bullpen, the D-backs wanted pitchers that gave opposing hitters different looks. Bradley mainly features his fastball and curve, while Boxberger is a fastball/slider guy. Hirano, who signed out of Japan for two years and $6 million, relies on a fastball-split combo.
The bullpen is also versatile, with Bradley being able to throw multiple innings if need be. Chafin can get righties and lefties out, so he's not strictly a situational guy, while Delgado -- if healthy -- can spot start or fill the long role in the bullpen as well as get big outs in the middle innings.

QUESTION MARK
Fernando Rodney drove some D-backs fans nuts with his tendency to make even successful saves appear interesting, but the fact is the right-hander did get the job done most of the time. His veteran presence also helped mentor young relievers like Bradley and Sherfy.
With Rodney now gone via free agency, the team has a hole at the closer spot. Bradley, Boxberger and Hirano are all candidates for the role. Boxberger is the only one of the three with Major League experience closing games (44 career saves), and as other teams have learned through the years, it isn't always a seamless transition from setup man to closer.

WHAT MIGHT CHANGE
Projecting a bullpen before Spring Training even opens is at best a shot in the dark. For instance, last year Bradley was viewed as a starter right up until the last week of camp.
The first order of business will be determining a closer. It is next to impossible to have a closer competition during the spring because you can't simulate the adrenaline and importance of the ninth inning of a spring game. Plus, especially early in camp, the hitters in the ninth inning are typically a team's younger or non-roster players.
With all that in mind, it will be interesting to see how the D-backs handle things this spring.
Delgado missed half of last season due to a flexor strain in his elbow, and he underwent a platelet-rich plasma injection in September. A follow-up MRI showed progress, and the team hopes he's healthy for Opening Day.
If Delgado is not, that could open the door for someone like Braden Shipley, who has started in the Minors but could be valuable in the bullpen. Shipley would be able to fill Delgado's role of the occasional spot start and long reliever.