The Nationals were swept by the Cubs on Sunday, but that's not what had pitcher Tanner Roark upset.

The Cubs walked Nationals right fielder Bryce Harper six times and also hit the 2015 National League MVP in Sunday's 4-3 win. Three of the walks were intentional.

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Roark, who struck out seven and allowed just one run on four hits in six innings, said the Cubs were afraid to pitch to Harper.

"I think it's scared baseball," he told reporters, adding he was "very, very surprised" the Cubs did not give Harper anything to hit.

Harper was walked 13 times during the four-game series. He's the first player since Barry Bonds in 2004 to draw at least 10 walks in a single series. Harper's six walks Sunday tied an MLB record and he became the first player in MLB history to reach base seven times without a single official at-bat.

Maybe even more surprising Sunday was that the Cubs pitched around Harper despite having ace Jake Arrieta on the mound. Arrieta allowed three runs over five innings with seven strikeouts and four walks — two to Harper.

But it worked as the Cubs completed the four-game sweep for their seventh straight win.