Lucas Giolito threw four scoreless innings in his rain-shortened major league debut, and the Washington Nationals beat the New York Mets 5-0 on Tuesday night.

Baseball's top pitching prospect allowed just one hit — a leadoff single — struck out one and walked two before a lengthy rain delay ended his outing. The 21-year-old Giolito threw 29 of his 45 pitches for strikes and was in command against the Mets like a seasoned veteran.

Bryce Harper hit a two-run home run, his team-leading 16th of the season, Wilson Ramos drove in two and Anthony Rendon had an RBI triple to provide the run support.

Mets right-hander Matt Harvey (4-10) was the hard-luck loser despite striking out three and allowing just four hits in 3 2/3 innings.

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