For half of the 2018 MLB regular season, Junior Guerra was the ace of the NL Central champion Milwaukee Brewers. Left off the Opening Day roster after a promising spring, Guerra was nonetheless called upon to make his first big league start of the year on April 11th. He delivered 5.1 innings of one-run ball at Busch Stadium against the St. Louis Cardinals, out-dueling Adam Wainwright as the Brewers won the game by a score of 3-2.
On July 8th, Guerra completed his 17th start of the season, six innings of one-run pitching in a 10-3 defeat of the Braves.