Source: Phils eyeing Jonathan Papelbon

The Philadelphia Phillies continued to show "serious" interest in longtime Boston Red Sox closer Jonathan Papelbon on Friday, as momentum toward a deal to bring back their incumbent closer, Ryan Madson, was disintegrating.

One source told ESPN.com that there was "serious interest on both sides" in a deal that would bring Papelbon to Philadelphia.

Meanwhile, another source said he now believes that an agreement with Madson, which had seemed close earlier in the week, was unlikely to happen at all.

It was still unclear exactly what caused the club's negotiations with Madson and agent Scott Boras to fizzle the past 48 hours.

But Phillies general manager Ruben Amaro Jr. vigorously denied an SI.com report that the two sides had agreed on a four-year, $44 million contract, pending the approval of team president David Montgomery.

"Number 1, we prefer that these negotiations be private," Amaro told ESPN.com. "Number 2, the rumors that are out there (of a deal) are unequivocally false. There was no agreement."

Amaro declined all further comment, other than to say "a closer is still a priority for us."

Sources familiar with the Phillies' thinking say the team's decision-makers have been debating the merits of keeping Madson, versus signing Papelbon to be their closer, for some time now.

But as it became increasingly clear that Papelbon's price might not be dramatically higher than the four-year deal Boras has been seeking for Madson, the club's interest in Papelbon has remained high, while the pursuit of Madson has waned.

Papelbon, who turns 31 on Nov. 23, is three months younger than Madson, but has a six-year track record as a closer compared to one for Madson, and is widely looked at as the top closer on the market.

Papelbon has racked up 219 career saves, compared with 52 for Madson, and has a substantially lower career ERA (2.33) and WHIP (1.02) than Madson (3.59 and 1.29, respectively), despite pitching his entire career in the AL East.

So if the Phillies are going to break their longstanding policy against giving out contracts longer than three years to any pitcher, track record is the factor that they have long weighed above any other.

After they made an exception to that policy by signing Cliff Lee to a five-year contract last December, one high-ranking Phillies official pointed specifically to Lee's track record, saying they would make that exception only in special cases where they could tell other pitchers looking for deals that lengthy that "you haven't had the career he's had."

One source said the Phillies have had "extensive negotiations" with Papelbon's agents, Seth and Sam Levinson, beginning just minutes after the free-agent negotiating period began at 12:01 a.m. ET Nov. 6.

The source said that while those negotiations have hit "some bumps in the road" since then, the team's interest in Papelbon "has never waned."

Papelbon is a Type A free agent, and no Type A free agent has changed teams this winter while the compensation rules governing premier free agents are being negotiated by players and owners at the bargaining table.

However, one source said he did not believe the labor uncertainty would affect the Phillies' pursuit of Papelbon in any way.

Nevertheless, Red Sox officials have said they would like to re-sign Papelbon, and the Toronto Blue Jays and Florida Marlins reportedly also have expressed strong interest.

Jayson Stark is a senior MLB writer for ESPN.com.