Ace Max Scherzer struck out a season-high 15 batters through 6 1/3 innings, but he will receive only a no-decision for his efforts in the Nationals' rubber game against the Phillies on Sunday afternoon.
Scherzer departed with one out in the seventh after throwing 111 pitches, 71 for strikes.
Matt Adams hit a second-inning solo homer to put Washington ahead, 1-0. But Nick Williams' pinch-hit single off reliever Sammy Solis in the seventh inning brought in a run charged to Scherzer to tie the game.
Williams was hitting in place of Phillies righty Jake Arrieta, who exited after allowing one run over six frames.
In a game during which both right-handed starters were dominant, Scherzer made history.
His 15 strikeouts are the most on record in MLB history in an outing of 6 1/3 innings or fewer.
At one point, the two-time defending National League Cy Young Award winner had fanned seven consecutive Philadelphia batters, the second-longest such stretch in the Majors this season.
Scherzer recorded 12 consecutive outs via strikeout before Maikel Franco grounded his 104th pitch into a double play to end the sixth.
Scherzer's strikeouts were his most since he became the fifth Major League pitcher to fan 20 batters in a nine-inning game. That feat came in a 3-2, complete-game victory over the Tigers on May 11, 2016.
He now boasts five games with 15 or more strikeouts over his career, including four since joining the Nationals in 2015.