PITTSBURGH — Jeff Samardzija pitched the Cubs’ first complete game in his final start of the season and Chicago beat the fading Pittsburgh Pirates 4-3 on Saturday night.

David DeJesus singled in Welington Castillo with two outs in the eighth for the go-ahead run after Pittsburgh had tied the game at 3 in the bottom of the seventh.

Samardzija (9-13) overcame a rocky first inning to allow two hits over his final 8 2-3 innings. With the 27-year-old in his first full season as a major league starter, the Cubs announced Friday their intention to shut him down for the season.

Batting in the No. 9 spot in the order, Chicago’s Tony Campana had two hits and scored two runs. Alfonso Soriano hit his 27th home run for the Cubs, who arrived in Pittsburgh having lost 17 of their previous 18 road games but won for the second consecutive night.

Pedro Alvarez two hits and two RBIs for the Pirates, who have lost six of eight and were passed by Los Angeles for third place in the NL wild card standings.

Samardzija had nine strikeouts, allowing four hits, one walk and two earned runs in his first career complete game.

Samardzija completes his season by pitching 174 2-3 innings — five more than he pitched over the course of his first four seasons in the majors combined.

Before the game, Cubs manager Dale Sveum said he would be more likely to stick with Samardzija deeper in the game because there was no need to save him for a future start. Samardzija threw a season-high 120 pitches.

He was not sharp to start the game, allowing a single to Brock Holt, hitting Andrew McCutchen and walking Garrett Jones before Alvarez’s single drove in Holt and McCutchen.

But Samardzija settled in after that hit, retiring the next eight hitters and 19 of the next 20 until Rod Barajas reached via a throwing error by shortstop Starlin Castro with two outs in the seventh and the Cubs leading 3-2.

Pinch-hitter Jeff Clement followed with a single off the wall in right, scoring pinch-runner Josh Harrison.

Just as he said, Sveum stuck with Samardzija — not only in facing Clement but in letting him hit the following inning with the go-ahead run on second and one out.

Samardzija grounded out, but Campana walked before DeJesus lined a single to right off Jason Grilli (1-5).

Alex Presley’s throw arrived at about the same time as Castillo, but Castillo’s nifty slide eluded Michael McKenry’s tag. Castillo had led off the eighth with a single.

Chicago got a run in the second, third and fifth innings. Soriano led off the second with his 27th homer, the most he’s had since 2008. It was his fourth home run in his past nine games.

Two days after the Cubs were involved in two dugout-clearing incidents against the Washington Nationals, home plate umpire Scott Berry warned both dugouts after James McDonald hit Anthony Rizzo with a pitch in the third. Samardzija plunked McCutchen in the first.

The Cubs’ Steve Clevenger learned early Saturday he would be serving a one-game suspension for his role in the Saturday’s game.

McDonald allowed three runs and seven hits in 5 2-3 innings.

Notes: According to STATS LLC., it was the seventh time in the majors this season a team hit the pitcher eighth. The Cubs had not batted a pitcher eighth since at least 1974 — the earliest such research is available. ... Cubs 2B Darwin Barney played his 124th consecutive errorless game at second base, setting an NL record. Barney’s streak surpassed 1,000 innings Saturday. ... Sveum termed OF Brett Jackson “day to day” due to a right knee injury sustained while crashing into the PNC Park outfield fence during Friday’s game. He won’t play until at least Tuesday.

... RHP Jason Berken will make his Cubs debut starting the Sept. 15 game against Pittsburgh. Berken was acquired off waivers from Baltimore on Friday. ... The Pirates announced their starters for their series in Cincinnati Monday-Wednesday: LHP Wandy Rodriguez, RHP Kevin Correia, RHP A.J. Burnett. ... Rookie left-handers start against each other in the series finale Sunday: The Cubs’ Chris Rusin (0-2, 9.00) and Pittsburgh’s Jeff Locke (0-1, 4.82).