Free agency is a time for opportunity, excitement -- and regret.
For every player looking forward to a bright future in a new home, for every team thrilled to be adding a shiny new piece, there is an organization left behind. And while many of the teams who lose men to the open market do so willingly (or, at least, knowingly), some will come to seriously miss the talent walking out the door -- even if they don't realize it just yet.
Below are six free-agent signees who will be dearly missed by their old teams, ranked according to the degree to which their absence will be felt this season:
1) Ndamukong Suh, defensive tackle
Last season, the hard-playing Suh accounted for 53 tackles, 8.5 sacks, three passes defensed and 29 pressures -- the kind of production from that defensive tackle spot you simply can't replace. Suh had a massive impact on the Lions' second-ranked defense, regularly attracting double- and triple-teams and thus opening things up for guys like linebacker DeAndre Levy, who had 151 tackles (second-most in the NFL), and Ziggy Ansah, who posted 49 tackles and 7.5 sacks in his second pro season.
Suh's presence was probably the biggest reason the Lions made the playoffs last season, and I think they're going to have a much more difficult time making it back without him. Recent trade acquisition Haloti Ngata is very good at the point of attack and a solid overall player, but I don't think he'll get as many sacks or pressures as Suh. He's more of a charge-straight-ahead guy, whereas Suh could make plays at the point of attack or outside and rush the passer. Defensive coordinator Teryl Austin did a heckuva job in 2014, but the entire unit is going to miss Suh, even the guys in the secondary like Glover Quin and Darius Slay, who had strong seasons in part because Suh forced quarterbacks to get rid of the ball sooner than they wanted to. Detroit will have a chance to compete, but the Lions face a tough road ahead.
2) Darrelle Revis, cornerback
Though he's obviously much smaller than the hulking Suh, Revis has a gargantuan effect on the field. Consider that, in three playoff games last season, Revis was targeted six times and burned just twice, allowing a total of 22 yards. The impact of someone who can put the clamps on the opposition like that -- especially in the postseason -- cannot be overstated. When you consider that Revis is playing at an elite level against the best and most sophisticated passing attacks in NFL history, his success is downright mind-boggling.
Revis knows how to really body-up receivers. He also has very strong hands in press coverage and is an outstanding tackler. Nobody throws in his direction. He helps whoever is at the opposite corner spot and enables the defense to be tilted. Of course, Patriots coach Bill Belichick excels at scheming his defense to take the opponent's best player out of the game no matter who's on his roster, and I think New England will still be able to do that to some degree -- but not to the extent it could when Revis was in the fold. The Pats will continue to win, but I think the distance from No. 1 to No. 4 in the AFC East has shrunk a bit.
3) DeMarco Murray, running back
It's easy to say the Cowboys can just run anyone out there behind their stellar offensive line and be fine. And the fact is, they'll probably be able to find a back -- perhaps such as free-agent acquisition Darren McFadden, who does have talent -- capable of putting up 1,100 yards or so. But I don't think that substitute will be able to generate the big, chain-moving plays at the rate that Murray could, or catch the ball as well as Murray. When you have a first-down machine like Murray (who had an NFL-best 85 rushing first downs in 2014), you can keep your defense off the field longer, which is a huge advantage.
I understand why the Cowboys might have been willing to let Murray walk, because you don't want to mortgage your future. But the fact is, Murray -- who out-produced flashy fellow back LeSean McCoy in multiple categories last season, including yards (1,845 to 1,319), rushing touchdowns (13 to five), yards per carry (4.7 to 4.2) and runs of 10-plus yards (45 to 34) -- will be difficult for Dallas to fully replace.
4) Julius Thomas, tight end
Thomas was limited to 10 starts in 2014 -- but he still pulled down 12 touchdown catches, giving him 24 over the past two seasons. That kind red-zone production is obviously special, and the Broncos will sorely miss what Thomas was able to do there. He's a huge guy, body-wise, a 6-foot-5, 250-pound target who is very difficult to guard in the end zone. He also had seven big plays (those that went for 20-plus yards), and 30 of his 43 receptions were considered "clutch catches." He dropped just two passes out of 62 targets.
5) Andre Johnson, wide receiver
The Texans needed cap space heading into the offseason, and the 33-year-old Johnson just posted his worst yardage total out of any season in which he played at least 15 games. But a deeper look at the numbers reveals a veteran receiver who will be difficult to fill in for following the team's decision to release him. Sure, he had just 936 yards and three touchdowns -- but he also recorded 14 receptions of 20-plus yards and just four drops out of 147 targets, which is pretty good.
The presence of rising youngster DeAndre Hopkins might have made Johnson seem expendable, but one of the biggest things the veteran did last season was enable Hopkins to catch more passes and be more productive, simply by virtue of absorbing some defensive attention. Will Hopkins be as effective with Cecil Shorts as his running mate? Bill O'Brien is a good coach, and his team has a chance to increase its win total over last season -- but if that happens, it'll probably be because of Houston's defense more than anything else.
6) Rodney Hudson, center
I don't think people realize how important a guy like Hudson can be. He wins with quickness, execution, work habits and football smarts. Hudson is a bit undersized, but he makes up for it with his ability to get his body on someone. He's also a good zone blocker. Hudson is a special player, someone who reminds me of Hall of Famer Dermontti Dawson. He might not be the biggest, but he's athletic enough to get out on the linebackers; he can pull or do whatever you need. He's the kind of guy who gets taken for granted -- until he's gone.
Regardless of what the Chiefs do to replace him -- and you can't just slot another guy in there -- his loss will be hard to overcome. Kansas City might have a tougher time running the ball than it has the past couple of years. In fact, I think Hudson's absence might counterbalance the benefit of adding receiver Jeremy Maclin, with the team very possibly finishing around 9-7 again. Hudson was a leader, the first guy in the building in the morning and the first guy on the field at practice. He will be missed for his impact on and off the field.