Matt Barnes, his curveball, and a case for him to be Red Sox’ closer in 2019

Matt Barnes punched out 14.0 batters per nine innings and posted one of the higher ground-ball rates in the game in 2018.Jim Davis/Globe staff

What if the Red Sox could have Craig Kimbrel for about $1.5 million next year? In a way, they will.

In 2018, a strong case can be made that Kimbrel wasn’t the best reliever on the Red Sox. Yes, he was the pitcher who helmed the ninth inning for 42 saves, but his 13.9 strikeouts per nine innings came with 4.5 walks per nine innings, a career-high 1.0 homers per nine innings, and a career-low 28.2 percent ground-ball rate.

Aside from the saves, Matt Barnes had a very similar season. Like Kimbrel, he struck out 96 and walked 31; Barnes did so in 61⅔ innings, while Kimbrel accumulated those totals in 62⅓. Barnes punched out 14.0 batters per nine, walked 4.5, gave up fewer homers (a career-low 0.7 per nine), and posted one of the higher ground-ball rates in the game (53.0 percent).

In other words, Barnes allowed contact with roughly the same frequency as Kimbrel, while the kind of contact that he allowed proved less damaging.

Though Barnes posted a higher ERA (3.65 to Kimbrel’s 2.74), the frequency and quality of contact suggest that he had the better year. In many ways, Barnes was one of the best relievers in baseball, particularly outside of the August stretch during which a hip injury affected his command and pitch movement. Although his walk rate is fairly subjected to scrutiny, the 28-year-old limits the damage from free passes by striking out loads of hitters and permitting few hits.

Barnes’s emergence gives the Red Sox flexibility. President of baseball operations Dave Dombrowski identified Barnes and Ryan Brasier as two internal candidates to close, and in the case of Barnes, the mere fact of his consideration for the role is a reflection of his steady evolution and improvement.

Barnes isn’t the pitcher he was when he made his big league debut in 2014, nor is he the pitcher he was in 2015 and 2016. He has altered his pitch mix in a way that has allowed him to become increasingly effective, a development perhaps best embodied in Game 2 of the ALCS against the Astros.

Barnes entered with two on and two outs in the top of the fifth inning, the Sox clinging to a 5-4 lead and down, 1-0, in the series. An extra-base hit would put their season in jeopardy.

But Barnes struck out Marwin Gonzalez, then blitzed through a perfect sixth inning, totaling 15 pitches — of which a startling 14 were curveballs.

The outing offered a marker of Barnes’s mid-career transformation.

He emerged as a first-round pick in 2011 and as a highly regarded prospect in 2012 based solely on his ability to blow fastballs past hitters. As for his breaking ball . . .

“You saw it coming up,” Barnes saud. “If you needed someone to throw a curveball in the lefthanded batter’s box, I was your guy. For one reason or another, I couldn’t wrap my head around throwing a curveball.”

But one day during batting practice in Double A in early 2013, Barnes had a conversation with longtime teammates Brandon Workman and Anthony Ranaudo about curveball grips. They encouraged him to try a spike grip, and it took, getting better and better over time.

In 2018, Barnes threw his curveball just more than 40 percent of the time — almost doubling his usage rate in 2015 — and showed the ability to dominate with the pitch, getting huge numbers of swings and misses while giving up almost no extra-base hits.

The combination of a swing-and-miss curveball with a fastball that averaged 97 miles per hour and likewise missed bats at the top of the strike zone suggests a pitcher who has emerged as an excellent — perhaps even elite — reliever. As the Twitter account Red Sox Stats notes, the Red Sox used him accordingly in the postseason, when he was their most trusted reliever in high-leverage situations.

That emergence, in turn, helps explain why Barnes, whom MLBTradeRumors.com projects to earn $1.5 million in 2019 as a first-time arbitration-eligible player, is quite reasonably in the conversation as a closer for the Red Sox if Kimbrel doesn’t re-sign (likely) and they don’t add a closer from outside (less likely).

Of course, the fact that the Red Sox have the luxury of considering Barnes as a successor to Kimbrel doesn’t mean that they can stand pat with their bullpen. If, for instance, Barnes becomes the closer, then the club would have to account for his absence — and perhaps that of free agent Joe Kelly — from the middle innings.

Nonetheless, even as the Red Sox are confronted with the potential task of restructuring their bullpen post-Kimbrel, Barnes gives them a solid foundation from which to work. They will have to add and reload to the relief core, but with Barnes in either a versatile setup role or at the end of games, they won’t be starting from scratch.