CHICAGO (AP) -- Jon Lester doesn't get wrapped up with who he is pitching against. The Chicago Cubs ace knew against Washington's Max Scherzer, he couldn't afford any mistakes.
He made one.
Bryce Harper hit his 18th home run, Scherzer struck out a season-high 13 to outduel Lester and the Nationals beat the Cubs 3-0 on Wednesday night.
The top two free-agent pitchers on the market last offseason, Scherzer (6-3) and Lester faced off in a memorable matchup in the finale of the three-game series. Scherzer, who signed a seven-year deal worth $210 million, was better than his counterpart, throwing seven scoreless innings while allowing five hits and one walk to win his fifth straight start.
For Lester, giving up Harper's home run proved a costly error.
"The thing that makes really good hitters is when you make mistakes, they don't miss them," Lester said. "That was really the only mistakes I made to him all night."
Scherzer and three relievers combined to shut out the Cubs and take two of three from Chicago. Drew Storen pitched a scoreless ninth for his 16th save in 17 attempts.
In support of Scherzer, Harper continued his torrid May and pulled even with Seattle's Nelson Cruz for the major-league lead in homers. Harper's sixth-inning home run off Lester (4-3) was a line drive into the left-field bleachers, giving him 13 this month and 28 runs batted in during May.
It proved to be enough for Scherzer.
"He's unbelievable," Harper said "He's definitely as good as advertised."
Matt Grace started the eighth for Washington and allowed a Jorge Soler double and hit Anthony Rizzo before being replaced by Casey Janssen. Janssen got Kris Bryant to pop out before Dexter Fowler's sacrifice advanced the runners to second and third. Starlin Castro then grounded to short to end the threat for the Cubs, who lost for the fourth time in six games.
Danny Espinosa added a solo home run in the ninth off Travis Wood.
Beyond Harper's home run and an unearned run in the fourth, Lester kept pace with Scherzer. The veteran left-hander, who joined the Cubs after signing a six-year, $155 million contract, went seven innings and allowed two runs (one earned) and seven hits while matching a season-high with 10 strikeouts but couldn't become the first Chicago pitcher to win five games in a calendar month since Carlos Silva in May 2010.
As good as Scherzer was, Lester resisted the urge to try and match him pitch-for-pitch while trying for his fifth straight win.
"For me, I've got to take a game the same as I do a game against Max," Lester said. "I can't do the roller coaster ride."
THANK THE FANS
Bryant was second among National League third basemen in a balloting update released Wednesday. Bryant had 583,583 votes, behind St. Louis' Matt Carpenter (1,113,060). "Cubs fans are the best in baseball, so I think anybody that's on the Cubs has a good support system around them," Bryant said.
Nationals: RHP Doug Fister (right forearm tightness) began the first day of a throwing program by playing catch Wednesday. Fister was placed on the disabled list May 15. . IF Anthony Rendon (strained oblique) played five innings in a simulated game in what manager Matt Williams referred to as a positive sign.
Cubs: Soler didn't start, but manager Joe Maddon said that was to give him an extra day off before Friday's series opener with Kansas City.
Nationals: RHP Stephen Strasburg (3-5, 6.50) faces Reds RHP Anthony DeSclafani (2-4, 3.46) on Friday in Cincinnati. Strasburg hasn't pitched more than 3 2-3 innings in three of his previous four starts
Cubs: RHP Jake Arrieta (4-4, 2.95) faces Kansas City RHP Edinson Volquez (4-3, 2.77) at Wrigley Field. Arrieta has been strong at home, posting a 2.41 ERA in five starts at Wrigley.