If only Frank Wren could go back in time and direct the managers in the Atlanta Braves' farm system to pitch Craig Kimbrel in more multiple-inning increments, maybe there wouldn't be so much discussion of how the Boston Red Sox are choosing to deploy their closer this season.

Then again, there's really nothing conventional about the way Kimbrel has been used, now or in the past.

Wren was the Braves' general manager when they drafted Kimbrel in 2008 and put him on an unusual development path. While most contemporary closers, including the great Mariano Rivera and Trevor Hoffman and even Aroldis Chapman, were starting pitchers at the outset of their minor league careers, Kimbrel was a late-inning reliever from his very first game in rookie ball.

Every one of Kimbrel's 121 minor league outings before his last big league call-up in 2010 came in relief. Of those, 80 were one-inning appearances. The hard-throwing right-hander completed a second inning 24 times, only eight of which came at the Double-A or Triple-A level.

Kimbrel was bred to be a closer, plain and simple, and a one-inning closer at that.

It's no wonder, then, that Red Sox manager John Farrell's recent usage of Kimbrel is raising eyebrows across New England. Entering the weekend, Kimbrel had been asked to get more than three outs in three of his past four appearances and five times overall. That's as many multiple-inning appearances as he made all of last season, and only five fewer than in his first six big league seasons combined.

Kimbrel has been so dominant that Farrell can hardly be blamed for calling on his closer as often as possible. Entering Saturday, Kimbrel had recorded a 0.98 ERA, 18 saves in 19 chances, 55 strikeouts and only five walks, while averaging 17.9 strikeouts per nine innings. His average fastball velocity has been 98.1 mph, an increase over his career average of 96.8 mph, according to data from FanGraphs.

But, well, if the Red Sox keep using Kimbrel like this, isn't there a danger of burning him out?

"Seemingly, he enjoys it. He does enjoy doing that," pitching coach Carl Willis says. "I do think, however, it's something we have to be careful of. We did it three times on the [recently completed 10-game] road trip. I don't think from a physical standpoint that it's going to affect him long term, as long as we can manage it a little better and not do it as often."

It's convenient, too, that Wren now works for the Red Sox as a senior vice president of player personnel.

Wren signed off on the Braves' plan to develop Kimbrel exclusively as a reliever. Like most of Atlanta's scouts, Wren always viewed Kimbrel as the mirror image of All-Star closer Billy Wagner in terms of both their stature and their stuff. The Braves weren't wrong. Kimbrel's numbers through age 29 -- 1.81 ERA, 273 saves, 14.7 strikeouts per nine innings -- are even better than Wagner's at the same point in his career (2.73 ERA, 146 saves, 13.1 strikeouts per nine).

"At the time, I think the preferred development path for even relievers was to give them multiple innings to allow them to develop their pitches," Wren says. "But I think that's what was exceptional about Craig. It was pretty universal in our thought process that we will try to get him multiple innings at times, but this guy is a closer."

Kimbrel isn't alone in his one-track path through the minors. Chad Cordero and Huston Street weren't starters in the minors before becoming closers in the big leagues. Former Baltimore Orioles closer Gregg Olson might have blazed the trail when he was drafted and quickly developed as a closer in the late 1980s.

But since Kimbrel made his major league debut in 2010, closers have been asked more frequently to get four- and five-out saves, a request that is more difficult for a pitcher who is unaccustomed to going more than one inning. Wren says he has discussed the topic with Kimbrel only once, after the Braves were booted from the 2013 playoffs by the Los Angeles Dodgers in an NL Division Series game in which Kimbrel remained in the bullpen in the eighth inning while David Carpenter gave up the go-ahead homer to Juan Uribe.

"I remember he said he felt like he was very comfortable being used in more than an inning, more than three outs," Wren says. "Now, we probably didn't do it with him as much as we would've liked [in the minors]. It's one of those situations where we're seeing that role evolve some. I don't know how far it's going to evolve, just because no one can hold up being used multiple innings that often at this point just because we haven't been trained that way."

Farrell is acutely aware of Kimbrel's relative lack of experience in multiple-inning situations. It's the biggest reason he admits he feels uneasy about bringing Kimbrel into the eighth inning as often as he has.

"It's been five times now, which is a high number," Farrell says. "I'll be honest with you, there's reluctance on my part to continue to do that. When we've done it previously, there's usually been a day or two following where he's been down. He's extremely valuable, he's incredibly talented and will closely be monitored every time he walks to the mound."

In 25 appearances this season entering Friday, Kimbrel had thrown 413 pitches. At the same point last season, he had thrown 390. He has had eight outings of at least 20 pitches, including three with 30 or more. But Kimbrel has pitched three days in a row only once. And there has been only one time when he pitched the day after throwing 20 or more pitches.

Kimbrel says his arm has felt fine. But he also admits he prefers pitching one inning several days in a row rather than multiple innings every few days. After all, it's the only thing he knows.

"I mean, I've thrown one inning my whole career," Kimbrel says. "It's something I'm still getting used to. It's still a learning thing for me. In a perfect scenario, I face one guy in the eighth and three guys in the ninth, and my pitch count won't get up there. But it's not going to be like that every time."

It hasn't been like that very often during Kimbrel's career. So, although it might be tempting, the Red Sox will be mindful of not pushing him too far.