The Chicago Cubs clinched a playoff spot under rookie manager David Ross, returning to the postseason after a one-year absence despite losing to the Pittsburgh Pirates 3-2 Tuesday night on a walk-off home run by Jacob Stallings.

The Cubs began the day with a 4 1/2-game lead over St. Louis and Cincinnati in the division standings and a magic number of four to clinch the title. Chicago missed the playoffs last year for the first time since 2014.

Stallings connected with one out in the ninth inning off Andrew Chafin (1-2) to help the Pirates end their five-game losing streak and win for the just second time in 15 games. It was Stallings' third home run of the season and the third game-ending hit of his career.

Chafin got the final out of the eighth and first of the ninth before Stallings sent a 2-2 pitch down the left field line and into the bleachers. The Pirates' shouts of joy echoed over throughout the empty ballpark.

Anthony Rizzo's two-run homer in the eighth inning had pulled the Cubs into a tie at 2-all.

Richard Rodriguez (3-2) pitched a scoreless ninth for the win.

Chicago's Jose Quintana was activated from the injured list and made his first start of the season. The left-hander went two innings and gave up one run and one hit with one strikeout.

Pittsburgh starter Steven Brault pitched seven shutout innings. He threw a two-hitter to beat the Cardinals in his previous start last Thursday.

Kyle Hendricks (6-4, 2.93) will start Wednesday night in the third game of the four-game series. He has allowed just seven walks in 73 2/3 innings this season.

Trevor Williams (1-8, 6.70) has lost five straight decisions since getting his lone win Aug. 13 at Cincinnati.