The sides had until 4 p.m. ET on Monday to hammer out a long-term contract since the Patriots had placed the franchise tag on Welker, which he already had signed.
Without a new deal, Welker will earn a guaranteed $9.5 million in 2012. If the Patriots decline to tag him next year, he will become an unrestricted free agent.
Welker arguably had his best season in 2011, catching 122 passes for a career-high 1,569 yards and nine touchdowns, which also was a personal best. However, a dropped pass late in Super Bowl XLVI tarnished the campaign.