Jim Riggleman resigned from his post at the helm of the Nationals on Thursday.

The Nats moved to 38-37 after a 1-0 victory over the Mariners on Thursday -- giving the club 11 wins in its past 12 games -- but Riggleman was unhappy that Washington's management had shown no interest in picking up the option year on his contract, according to Riggleman's agent, Burt Rocks.

"If you're going to do this job you have to be totally committed to it and feel like there's a commitment to you, and I just didn't feel that way," Riggleman said. "I've talked to [Nationals GM Mike Rizzo] in the past about addressing my situation, and it wasn't the right time, and I just felt it was worthy of a conversation."So it's been brewing for a while but I just felt that, I know I'm not Casey Stengel, but I feel like I know what I'm doing. But I felt like I shouldn't continue on with such a short leash where every little hill and valley is life and death in the game. The game's not fun that way. I just wanted to have a conversation in Chicago and [Rizzo] said he wasn't ready to have that conversation, so I said I have to give it up then."

Rizzo addressed the media shortly after the announcement.

"He told me of his displeasure of his contract situation, and that if something wasn't done about the contract situation by the end of the game he would resign," Rizzo said. "We accepted his resignation. As you can see it's taken us by surprise. We don't have an immediate plan for a successor ... will have an answer, someone will be managing the team.

"By no means is there no leadership or a person in charge of the organization. We feel we're going in the right direction, we continue to feel that way, the leadership is very very strong and committed to putting a winner on the field, championship-caliber organization.

"This is very disappointing, disappointing to the players in the clubhouse, the fanbase and to myself. But we will move on. As we have from the Strasburg injury, the Ryan Zimmerman injury, we will move forward and not miss a beat."

No interim manager has been named, though a decision is expected shortly. The club will decide who will skipper the team Friday sometime before its game against the White Sox.

"We have discussed his option being picked up several times during the season. I felt the time wasn't right to pick up the option, and certainly today's conversation, the way it was put to me, you certainly can't make that decision in a knee-jerk reaction," Rizzo said. "It's too big of a decision to be put in that position."

Riggleman, 58, is in his 12th season managing a big league team, and has an overall 662-824 record. He's also managed the Padres, Cubs and Mariners. He took over the Nats' job in 2009, taking the reins from Manny Acta, who is now the Indians manager.

"The timing of it, that he resigned at this time when we're playing so well, coming off a homestand we should be celebrating, coming off a great month of baseball, I'm disappointed that this is a distraction," Rizzo said. "That this is not thinking of the team first, it's thinking of personal things first. That's what disappoints me the most."

Riggleman is the second NL East manager to resign in the past week. Marlins manager Edwin Rodriguez resigned on Sunday.