To understand why the Patriots are comfortable letting Wes Welker walk to Denver while replacing him with Danny Amendola, you have to go back to March 2007 and appreciate what led the Patriots to Welker in the first place.
When Bill Belichick dealt second- and seventh-round picks to the Dolphins to acquire Welker in 2007, he wasn't bringing in a player with much of a pedigree. Welker went unselected in the 2004 draft, and while he made the Chargers out of training camp, San Diego cut him after the opening week of the season. Every team in the league got a second chance to acquire Welker for free, and each of them passed. Welker cleared waivers and made it to the Dolphins, where he spent one year as a returner and special teams grunt before eventually working his way into regular offensive reps. Unable to beat out the immortal Chris Chambers and Marty Booker for spots in a below-average passing attack, Welker started just three games during his three seasons in Miami. He caught 96 passes for 1,121 yards and one touchdown. Not in his last year. Across all three years.
Belichick treats second-round picks like they're manna from heaven, and he dealt a second-rounder and a seventh-rounder to the Dolphins to acquire Welker.1 Don't look back at that decision with what we know about Welker now; look back at it with what we knew about Welker at the time. He was hardly a sure thing; he was a receiver perceived to be a situational player with limited upside, Brandon Stokley with a fumbling problem (12 on 390 touches in Miami, a total that he matched over 817 touches with New England). Belichick didn't sign Welker for what he was. Belichick signed Welker for what he thought Welker could be.
Forgive me for sounding like Amendola's agent again for a moment, but his professional résumé before joining the Patriots simply blows Welker's pre-Pats career away. There are some similarities, of course. After the career at Texas Tech, Amendola went undrafted and became a practice squad guy, bouncing around the Cowboys and Eagles for about a year before eventually catching on with a bad team. The Rams used Amendola as a return guy before pushing him into the lineup as a situational receiver out of the slot. Unlike Welker, Amendola was the focal point of the Rams' passing attack, leading them in most receiving categories (including targets) in 2010. After missing virtually all of 2011 with a torn triceps, Amendola's 11-game season in 2012 prorates out to a 91-catch, 968-yard campaign. He'll join the Patriots with more than twice as many career catches and nearly twice as many yards as Welker had when he joined. He also won't cost the team a draft pick and has just $10 million guaranteed on his five-year deal, which is less than what Welker received as part of his two-year pact with the Broncos.
The biggest dig on Amendola is his health, but even that's been distorted in the analyses I've seen of this swap. Amendola suffered one major season-ending injury during his time with the Rams, a dislocated elbow. Over that same four-year stretch, Welker suffered one major season-ending injury, a torn ACL against the Texans. Amendola had the misfortune of suffering his injury in Week 1, while Welker's injury came during Week 17, allowing him to recuperate during the offseason before returning (as a limited version of his former self) without missing any regular-season games. This should go without saying, but you don't get to choose when you go down with a season-ending injury. The timing of each player's injury means something in terms of their past availability for their respective teams, but those two injuries are of equal relevance in predicting their future availability for their new teams. In fact, if anything, the Welker injury is scarier; a torn ACL for a player in his early-30s is much more worrisome than a dislocated elbow2 for a player in his mid-20s. Signing Amendola also doesn't preclude the Patriots from drafting another slot receiver in the late rounds (or signing one as an undrafted free agent) and attempting to develop him into a possible replacement if Amendola does go down with an injury.
What this eventually boils down to is the innate fear of change that fans have with regard to their team's stars. Most people are loath to give up on something good until it's been proven that a once-productive player can no longer perform at the same level. That's understandable, but it's a terrible way to run a football team. Belichick knows that, and he's spent 13 years moving on from players at exactly the right time. Patriots fans probably remember the case of Lawyer Milloy, who was released just before the 2003 season before catching on with the Bills and leading them to a 31-0 victory over the Patriots in Week 1. The Patriots went 17-1 after that and won the Super Bowl. When it wasn't Lawyer Milloy, it was Randy Moss. Or Ty Law. Or Richard Seymour. Or Deion Branch. Or Adam Vinatieri.3 At some point, Belichick might deserve the benefit of the doubt in these situations.
This all shouldn't really be much of a surprise. Belichick has had two years to give Welker a long-term contract and hasn't expressed even the slightest bit of interest in doing so. Having reportedly been given the final shot at matching what most people characterize as a modest two-year deal from the Broncos, Belichick turned the opportunity down. The Patriots are not built on getting every last drop out of their older players until they can no longer go. They've been built by having one constant — Tom Brady — and otherwise relying on change. They're the team that drafted one guy with a bum back and another who couldn't stop smoking weed and turned them into the most devastating set of tight ends in league history, a one-two strategy that teams around the league have tried to emulate since. They're the team that bought low on Moss and went to a scheme with spread characteristics before anyone else in the league had the balls to do so. And they're the team that went after Welker when he was a backup on a bad offense and ended up getting 672 catches and five Pro Bowls of output before moving on. Welker will very likely play well in Denver, as he'll spend two years catching passes from Peyton Manning in an offense that might even suit him better than the one he's leaving. But the Patriots will do just fine without him. They always do.