The righty won his four previous starts and flirted with no-hitters in his last two. Arrieta carried a perfect game into the seventh inning on June 24 against Cincinnati and went 7 2-3 innings without allowing a hit at Boston on June 30.
Washington ended such hopes immediately. Span hit a fly ball that sailed over the outfielders for a double leading off the first. One out later he scored on Jayson Werth's groundout for a 1-0 lead.
Arrieta allowed four hits and one run over six innings with three walks and five strikeouts. He gave up two singles to open the fifth, but escaped the jam. Zimmermann struck out while attempting to bunt the runner over.
"It was a dogfight," Arrieta said. "I really had to grind it out there. I had guys on base. I had to make pitches in big situations. I was able to do that."
Storen entered having allowed only three earned runs this season and only one in 17 appearances since May 17.
The Cubs threatened in the eighth, putting runners at second and third with one out against Clippard, but didn't score. Pinch-hitter Wellington Castillo struck out looking, and Ryan Sweeney grounded out.
Justin Ruggiano, Anthony Rizzo, and John Baker all had two hits for the Cubs.
NOTES: The Cubs recalled RHP Blake Parker from Triple-A Iowa before the game. Parker takes the roster spot created by the trade with Oakland. ... Chicago hasn't announced who will replace Samardzija and Hammel when their rotation spots come up Wednesday and Thursday. Edwin Jackson (5-8, 4.99) will open the five-game series at Cincinnati on Monday against fellow RHP Mike Leake (6-7, 3.47). ... Nationals RHP Stephen Strasburg (7-6, 3.53) will face RHP Chris Tillman (7-4, 4.21) on Monday when Baltimore visits Washington.