ARLINGTON -- Paul Sewald’s flawless start to the playoffs came to an end at the worst moment.

After dominating through eight consecutive scoreless appearances, Sewald blew his first save opportunity and allowed his first runs of this postseason as the D-backs fell to the Rangers, 6-5, in 11 innings to drop Game 1 of the World Series on Saturday night at Globe Life Field.

Summoned by manager Torey Lovullo with a two-run lead in the ninth, Arizona’s closer issued a leadoff walk to Rangers No. 9 hitter Leody Taveras, setting the table for a dramatic game-tying two-run homer by Corey Seager with one out. Texas completed its comeback in the 11th, when Adolis García walked it off with a solo homer off Miguel Castro.

The old baseball adage that leadoff walks will come back to haunt proved true for Sewald. That’s why he was more upset about the free pass to Taveras than the first-pitch fastball clobbered by Seager, who entered the night hitless in five previous career at-bats against him.

“You have to try and get to the bottom of the lineup before the top comes up,” Sewald said. “That’s what made me frustrated with walking the No. 9 hitter. Seager’s one of the 10 best players in this league. You have to try to face him with nobody on there.”

Sewald recovered with strikeouts of Evan Carter and Austin Hedges -- with a hit-by-pitch and an intentional walk between them -- to keep the game tied. Left-hander Kyle Nelson then took over and turned in a scoreless 10th. But after Nelson retired Carter to begin the 11th, Lovullo went to Castro for a matchup he liked against a red-hot García, who earlier in the game had tied the record for most RBIs in a single postseason.

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Despite having an on-deck hitter in Hedges, who had not previously appeared for the Rangers this postseason until Game 1, Castro was allowed to pitch to García in the tight spot. The right-hander fell behind in the count early to García before surrendering the decisive blow on a 3-1 sinker left up in the zone.

“Castro, we talked about that for a couple of days, that being a favorable matchup for us if it came down to that,” Lovullo said. “[We felt] that he would be able to make pitches on him and try and prevent a little extension. It was just a middle-middle pitch and [García] did his job.”

Sewald, who watched the ending from inside the trainers’ room in the visiting clubhouse at Globe Life Field, couldn’t help but feel accountable for what transpired. Up to the point he entered the game, the D-backs seemed to be following the formula that has worked for them so often this October. They fought back from an early deficit to take the lead against postseason juggernaut Nate Eovaldi and got a solid outing from Zac Gallen, who after allowing two runs through his first four batters ended up limiting a potent Rangers offense to three runs in five innings.

“Those guys shouldn’t have been pitching after I pitched, so that’s on me,” Sewald said. “There’s no worse feeling in this game than being the closer and blowing a save opportunity at the last second. This team battled for eight and a half innings and had the lead. My job is to finish games when I get in there, and I did not.”

For a D-backs club that leans so heavily on its relievers and is expected to go with a bullpen day for Game 4, Friday night could have major implications for the rest of the series. Six relievers covered 5 1/3 innings. Kevin Ginkel, one of Lovullo’s most trusted high-leverage options, had to throw 28 pitches in a shaky eighth inning.

One encouraging development for Arizona’s bullpen could be the potential emergence of Nelson, who entering this series was probably considered the team’s third left-handed option behind Joe Mantiply and Andrew Saalfrank. Yet he got big outs against the top of Texas’ lineup in extras.

This resilient D-backs squad has proven capable of picking itself up from a knockdown like this before. But after its pitchers combined to walk 10 batters on Friday night, it’s clear that group will need to tighten things up on the mound if they want any hope of doing so again.

“You can't walk 10 batters in a World Series game and expect to hold them in the situation that we held them in,” Lovullo said. “It was a matter of time before something happened, and it did.”