Finding a good fifth can make life a lot smoother.
Just ask the Mariners, whose search for a final piece to their rotation could carry into and through spring training, which begins Feb. 14 when pitchers and catchers report for workouts at the club’s complex in Peoria, Ariz.
"Pitching-staff wise, we’d still like to add," general manager Jerry Dipoto said last Friday after pulling off a pair of trades affecting the rotation. "We do have a little bit of room to be creative.
"The resources have always been there for us to be aggressive when the opportunity arises."
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Another off-season packed with roster moves — 16 newcomers on the club’s 40-man roster — included deals that deleted Taijuan Walker and Nathan Karns from the rotation while adding Yovani Gallardo.
That leaves the Mariners with four locks in their five-man rotation, barring injuries, as the calendar churns toward their April 3 season opener at Houston: Felix Hernandez, James Paxton, Hisashi Iwakuma and Gallardo.
While Dipoto remains open to filling the void by adding another veteran starter, he also shows a willingness to fill the fifth spot through a competition among in-house candidates.
"I’ve always been of the mind-set," he said, "that (with) some portion of your starting rotation — your fifth starter — you have to be cultivating young players and giving them innings in order to sustain what you’re doing as a franchise."
Dipoto quickly ticked off six in-house possibilities for the final starting job, including lefty Ariel Miranda, who ended last season in the rotation after being acquired in a July 31 trade from Baltimore for veteran lefty Wade Miley.
Three other candidates came from off-season deals: right-handers Chris Heston, Rob Whalen and Max Povse. The two others rate among the organization’s top prospects: right-hander Andrew Moore and lefty Ryan Yarbrough.
Let’s handicap the field and note this: All six either have options remaining or aren’t yet on the 40-man roster. That means spring performance, rather than roster inventory, is likely to be the key factor in awarding the job.
***Heston, 28, was a Dec. 7 pickup from San Francisco for a player to be named later. He missed much of last season because of a severe oblique injury but was 12-11 with a 3.95 ERA in 2015 over 31 starts.
He has the most big-league experience in the group and, if he shows signs of his 2015 form, seems positioned as no worse than an early co-favorite.
***Miranda, who turned 28 on Tuesday, was 5-2 with a 3.54 ERA after arriving from Baltimore but failed to last six innings in six of his 10 starts. His breaking ball remains a work in progress, which could mean he fits better as a long reliever.
The Mariners want two lefties in a seven-man bullpen. Currently, they have one certainty in newcomer Marc Rzepczynski, a match-up specialist. Other candidates include Paul Fry and newcomers James Pazos, Zac Curtis and Dean Kiekhefer.
If any of those four produce a strong spring, club officials are more likely to view Miranda as a rotation candidate. Otherwise, he seems a good bet to start the season in the bullpen — or Triple-A Tacoma.
***Whalen, 22, came from Atlanta with Povse in a Nov. 28 trade for two minor-leaguers whose development had stalled: outfielder Alex Jackson and pitcher Tyler Pike.
Whalen made his big-league debut last season in going 1-2 with a 6.57 ERA in five starts after compiling a 7-6 record and a 2.40 ERA in 21 minor-league starts. He’s a long shot who seems more like to start the season at Tacoma.
Povse, Moore and Yarbrough face even longer odds this spring because none have yet pitched above Double-A. The likely April destination for each is either Tacoma or Double-A Arkansas.
Even so, some club officials contend all three have greater long-term potential than Heston, Miranda and Whalen.
***Povse, 23, is 6 feet 8 and 185 pounds. A third-round pick in 2014, he was 9-6 with a 3.36 ERA while making 26 starts at Hi-A Carolina (15) and Double-A Mississippi.
Baseball America ranks Povse as the organization’s No. 8 prospect and said he "evokes comparisons with Doug Fister as a…strike-throwing, ground-ball aficionado."
***Moore, 22, made rapid progress since his selection in the second round of the 2015 draft. He was 12-4 with a 2.65 ERA in 28 starts at Hi-A Bakersfield (nine) and Double-A Jackson (19).
Baseball America pegs Moore as the organization’s No. 6 prospect and said he "projects as a reliable back-of-the-rotation option." Moore was also picked as the organization’s minor-league pitcher of the year.
***Yarbrough 25, was a fourth-round pick in 2014 who went 12-4 with a 2.95 ERA in 25 starts at Jackson. He was picked as the most valuable pitcher in the Southern League.
Bob Dutton: @TNT_Mariners