Joe Maddon says that Nationals pitcher Sean Doolittle used an illegal delivery, which led to him arguing to the umpires. (1:53)

WASHINGTON -- Chicago Cubs manager Joe Maddon protested Saturday night's 5-2 loss to the Nationals, arguing that Washington reliever Sean Doolittle used an illegal delivery in the ninth inning.

The double toe-tap Doolittle appeared to use as he delivered the ball to home plate has been deemed illegal in the past, but umpires on Saturday did not force the left-hander to alter his delivery, much to Maddon's dismay.

"I said, 'If you guys don't clean it up, I'm going to protest the game,'" Maddon said after the game. "It's their rule, not mine. I didn't ask for it in the first place."

While the manager indicated he was protesting, by rule the team then has to submit its official grievance to the league within 24 hours, but sources told ESPN's Buster Olney that it's unlikely that the Cubs will follow through.

Maddon came out to argue after Doolittle's first pitch of the ninth inning -- a strike to pinch hitter Albert Almora Jr. Although the umpires huddled with each other, and then with Doolittle, they sided with the lefty while deeming his delivery OK.

"[Maddon] thought he was tapping his foot, which in itself is not illegal, and this all kind of stems from his pitcher being called on something that was a little bit different than what Doolittle was doing," crew chief Sam Holbrook said. "So in our judgment, Doolittle did nothing illegal at all."

Holbrook was referring to Cubs reliever Carl Edwards Jr., who was told in the second game of the season that he couldn't do his version of the double toe-tap. Recently, Mariners pitcher Cory Gearrin was also forced to change his delivery after warming up mid-inning.

"It's real simple," a somewhat exasperated Maddon said. "That's exactly what Carl was told he can't do. I was told that's an illegal pitch and he can't do it."

Edwards added: "I figured once it happened to myself, it would get around."

Maddon lodged his protest with one out in the ninth inning. Theoretically, if the Cubs then protested to the league and won, the teams would pick up the game from that point, as Doolittle retired the next two batters to earn the save.

Afterward, Doolittle was having none of what Maddon was trying to sell.

"In that moment, he's not doing anything other than rattle me," Doolittle told reporters, according to an mlb.com report. "It was kinda tired. Sometimes he has to remind people how smart he is."