By the numbers: Behind the D-backs’ 8-3 surge to .500

After a dismal start to the season, the Arizona Diamondbacks have surged over the last two weeks, going 8-3 in their last 11 games to pull their record to .500.

Now in third place in the National League West, the D-backs have jumped into the playoff picture. They are tied with the Milwaukee Brewers (10-10) and St. Louis Cardinals (4-4) for sixth place in the league, and have played more games than either of the other two.

Here are some numbers, both good and bad, that define Arizona’s last two weeks. All stats are as of Monday morning:

Two big signings

The two biggest offseason acquisitions on offense, Starling Marte and Kole Calhoun, have shined during this 11-game stretch.

Starling Marte is slashing .400/.438/.622, good for an OPS of 1.060.

His batting average of .400 is 11th-best in the majors, which fits in nicely next to David Peralta’s .415 (7th in MLB), Ketel Marte’s .383 (13th) and Nick Ahmed’s .359 (18th) during the same stretch.

Marte has two home runs and eight RBIs to go with his 18 hits and 11 runs scored.

Kole Calhoun’s average isn’t as prodigious, but his power numbers have been imposing. He’s one of 15 players in the league to have at least five home runs since Aug. 5.

He has 15 RBIs and two doubles while hitting .273 with a .659 slugging percentage.

Early-game woes

Most of the players mentioned in the previous section hit near the top of the lineup, but that doesn’t mean the early innings have been good for Arizona.

The Diamondbacks have struggled to put runs on the board. They’ve only scored runs in the first three innings in three of the 11 games, all of which were wins.

In four of the games, they have been hitless the first time through the order.

Only 25 of the 123 plate appearances over the first three innings have ended with the player reaching base, an on-base percentage of .203, the worst in the majors.

That number drops to .160 if you exclude the Aug. 10 outburst, in which Arizona had eight base runners and five runs over the first three innings.

Later game success

It’s the middle and end of the game where the D-backs’ offense has taken off.

After the first time through the order, Arizona turns it on. The team’s .361 batting average over the middle three innings is the best in the majors, as is the 31 runs scored.

The D-backs do it with smaller hits and power: The 34 singles leads the league over those innings, 11 doubles is tied for second-most, and seven home runs is tied for sixth-most.

The bats have tended to get even hotter as the end of the game nears.

Arizona’s 37 runs scored in the seventh, eighth and ninth innings over the last 11 games leads the league by a large margin. Its .369 batting average is the highest and one of just two teams above .300; its on-base percentage of .443 is the only one above .400.

That’s been much-needed, because the bullpen has made late innings tough on the D-backs.

The bullpen

The bullpen, to put it very kindly, has been barely good enough.

The group has a 5.52 ERA during the stretch, which is the 11th-worst in the majors, but it’s somehow the second-best in the NL West: The Rockies are at 5.77, the Padres make both look paltry with a 7.23 ERA, and the Giants top that with a catastrophic 8.79 number. The Dodgers are the best in the MLB by a rather large margin at 1.69.

In close late-game situations, the bullpen has faltered some but largely held it together. In six games that had a score within three runs in the seventh inning or later, the D-backs’ bullpen allowed a .392 on-base percentage and only shut out the opponent twice.

Yet Arizona is 4-2 in those games.

The relief pitchers have had to bail out the starters consistently this season. Despite general struggles, over the 11-game stretch, the bullpen is 5-1 and one of just five groups to have five wins during that time.

Archie Bradley has been strong overall. He has four saves in five appearances and only allowed runs in one game, the 7-6 win over the Padres on Saturday.

The fifth starter

Merrill Kelly’s ups and downs last season have been widely discussed: Over six starts in June, Kelly had a 2.75 ERA in 39.1 innings. Over six starts from July 23 through Aug. 23, he had a 9.20 ERA in 29.1 innings. Over his five starts in September, he had a 2.18 ERA in 33.0 innings.

Through four starts this season, Kelly has been phenomenal.

Focusing strictly on his two starts during this 11-game stretch, Kelly has given up just one run over 12.2 innings. He’s allowed a total of nine hits and two walks, a batting average below .200 and WHIP of 0.87.

This has helped to offset an injury from No. 1 starter Madison Bumgarner and the ineffectiveness of No. 2 Robbie Ray (while Kelly’s WHIP is top-20 among starters since Aug. 5, Ray’s is second-worst).

Simply pitching into the seventh inning in both games has given the bullpen some relief for the extra innings the relievers have put in for other games.

As far as the No. 5 pitcher goes, the D-backs couldn’t have asked for anything better. Especially considering Kelly wasn’t even supposed to be in the starting rotation back in spring.

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