SAN FRANCISCO -- Signaling their intention to explore free-agent alternatives for starting pitching help, the Giants declined Monday to pick up the $6.5 million option on Ryan Vogelsong's 2014 contract, casting the right-hander into free agency.

Left-hander Javier Lopez, who was eligible for free agency after excelling in relief for the past 3 1/2 seasons with San Francisco, also entered the open market as he and the club could not reach a deal before the exclusive negotiating period ended Monday at 9 p.m. PT.

Giants vice president and assistant general manager Bobby Evans sounded resigned to Lopez's full-fledged entry into free agency.

"We've been in discussions with Javier, but I'm really not prepared to give you an update on that," Evans said, speaking earlier Monday. "We're going to maintain contact and discussion but [he] could be entering the market and exploring his options. We still have interest in bringing him back but we'll have to obviously compete against the market."

Vogelsong, who received a $300,000 buyout, also remained eligible to re-sign with the Giants. But prospects for an accord appeared dim, based on the absence of communication between both sides as Monday's deadline approached.

"Contrary to other reports, there were no negotiations between the Giants and Vogelsong to this point," said Vogelsong's agent, Dave Meier.

"The door's open for discussions with Vogelsong but we're not actively talking right now," Evans said. "We're open to discussing ways to bring him back, but right now we're going to have some exploration of the market."

Though open bidding for free agents had not yet begun, speculation already linked the Giants to the likes of Bronson Arroyo, who has pitched at least 199 innings in each of the past nine seasons; Tim Hudson, the 205-game winner who's overcoming a fractured ankle; Dan Haren, who has won 10 or more games for nine consecutive years; and Ricky Nolasco, who reportedly drew interest from San Francisco last season before the club fell from contention.

None of these starters received one-year, $14.1 million qualifying offers from their former clubs. Signing a player who didn't prompt a qualifying offer will enable San Francisco to avoid forfeiting its first-round selection in next June's First-Year Player Draft.

Evans refuted the notion that the Giants, whose surplus of talented starters in the lower Minor Leagues are projected to reach San Francisco in approximately two years, would feel comfortable offering free-agent pitchers only short-term contracts.

"If you have too much of a preconceived notion as to what you can do, it can really limit your options," he said.

After experiencing an eventful and humbling journey through Pittsburgh, the Minors and Japan that lasted a decade, Vogelsong posted a 27-16 record with a 3.05 ERA for the Giants in 2011-2012. He made the National League All-Star team in 2011 and was the team's leading winner in the 2012 postseason (3-0). He slumped last season (4-6, 5.73), though he sustained a broken right hand May 20 when he was hit by a pitch from Washington's Craig Stammen and endured the physical erosion that befell almost every Giant who participated in the World Baseball Classic.

Evans said that not retaining Vogelsong immediately was "a tough call," adding that timing with free agency was an issue. It's easy to assume that once the Giants realized how many starting pitchers didn't receive qualifying offers -- Cleveland's Ubaldo Jimenez, the Yankees' Hiroki Kuroda and Kansas City's Ervin Santana were the only ones who did -- keeping Vogelsong became less of a priority.

"We're not sure exactly how the market's going to develop. We're not sure exactly what our options are," Evans said. "I think to explore those fully, we need more time, and unfortunately we had to make a decision today."

Vogelsong's possible departure from the Giants also increases right-hander Yusmeiro Petit's chances of making the season-opening rotation as the No. 5 starter. Petit finished 4-1 with a 3.56 ERA in eight late-season games in 2013.

Lopez, who earned $4.25 million this year, could command a more lucrative salary on the open market. He posted a career-best 1.83 ERA in 2013 and led the NL by allowing only 10.5 percent (six of 57) of his inherited baserunners to score. In 236 appearances as a Giant, Lopez was 14-4 with a 2.26 ERA, compared with 13-9, 4.37 in 393 games elsewhere.

If Lopez leaves, the Giants may turn their attention to left-handed alternatives in free agency such as J.P. Howell or Scott Downs.