On April 8, Yasmany Tomas singled home Chris Owings in the bottom of the ninth inning in Phoenix, giving the Diamondbacks a 3-2 win over the Cubs and putting Chicago a game out of first place in the National League Central, at 3-1, while the Pirates were off to an undefeated start.
The Cubs won the next day, while the Pirates lost. Returning to Wrigley Field, the Cubs moved into first place by beating the Reds. After sweeping that series, Chicago was three games up on Cincinnati and St. Louis.
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The lead was up to six games after a win on May 4, then nine games after a win on May 14.