But after a slow first month starting in place of Maclin, Cooper has become one of the Eagles' most productive players on offense over the last eight games. His rise has coincided with that of quarterback Nick Foles, who has targeted only DeSean Jackson more (52 to 51) over that span.
Cooper's stock has spiked. Chip Kelly has gushed about the 26-year-old receiver, who has certain attributes that seemingly fit the Eagles coach's scheme, but free agency is tricky and the Eagles have another contract decision to make with Maclin.
"I want to be back here," Cooper said. "Everyone around here knows that I love the scheme. I think I fit in it well with the bubble screens and the stuff that we do with blocking and being a bigger guy and a bigger target."
It's unclear how the offseason incident in which Cooper was caught on video using a racial slur will affect his market. One NFL executive, who spoke on the condition of anonymity because Cooper was under contract with the Eagles, said that the receiver's use of the slur would give him pause when considering whether to offer a contract.
"Doesn't mean I wouldn't do it," the executive said.
Maclin's contract also expires in March. The Eagles' 2009 first round draft pick has a more accomplished NFL resume than Cooper, but Maclin has torn the anterior cruciate ligament in his right knee two times. By the end of this season, he will have missed 21 games over five seasons because of injury.
The Eagles certainly could decide to bring both back, especially if Maclin gets nothing more than one-year offers. Maclin's loss has been Cooper's gain. After catching only eight passes for 93 yards and a touchdown in the first five games, Cooper has tallied 29 receptions for 621 yard and six touchdowns since.
Jackson, over that same eight-game span, caught 37 passes for 555 yards and five scores.
"You never want to see someone go down and Jeremy is one of my best friends," Cooper said. "But when he went down someone had to step up and help this football team, and I kind of took it upon myself - 'How about you be the one?' "
Cooper, who doesn't have Jackson-like speed but is deceptively fast, is averaging 19.3 yards a catch, which ranks second in the NFL. Kelly said that the 6-foot-3, 222-pound Cooper's background in baseball and being able to track fly balls has aided his deep-ball skills.
Kelly cited Cooper's "ability to adjust to the ball and the ability to understand leverage of the defensive player and the ability Riley has of being big enough not to get knocked off-track when obviously the defensive player knows where the ball is going, too. But your ability to hold that line is a huge component."
CHIP THE PLAY-CALLER
Chip Kelly's offense is right there on television every week for viewers to watch and now on NFL.com for fans to dissect, using the coach's film if they pay a yearly fee.
But what kind of play-caller is the Eagles coach?
"I think all play-callers tend be quick thinkers," Eagles offensive coordinator Pat Shurmur said, "which of course he is."
Kelly's up-tempo offense can often move at a frenetic pace. To speed up the process, plays are sent in via one word or two- or three-word phrases. But Kelly always seems to be one step ahead of opposing defensive coordinators.
"It's just his feel for the game," Eagles quarterback Michael Vick said. "I don't think he purposely tries to be fast with his play-calling and his tempo. I think he just knows exactly what he wants next and that's what makes him so efficient."
As much as Kelly says his play-calling counters how a defense schemes his offense, practice squad quarterback G.J. Kinne said his secret is in the week of preparation before a game.
"We go over so much what we're going to do, we almost know what he's going to call," Kinne said. "He gives [starting quarterback] Nick [Foles] a lot of confidence out there because we've rehearsed so many times and he's right on with his calls."
Kelly first started calling plays in 1999 when he was in his first season as the offensive coordinator at New Hampshire. Like any skill, it developed over time. His meteoric rise from New Hampshire to Oregon to the Eagles suggests that he must be improving, but he was recently asked if he liked where he was as a play-caller.
"I'd better like where I am now, because this is where I am," Kelly said. "I've always believed play calling is based on your personnel. You're trying to get your players in positions to make plays, and you have good days and bad days, just like players have good days and bad days."
Kinne said that Kelly had a rare gift for being able to read a defense from the sideline. While all play-calling head coaches work from the sidelines, the NFL has more offensive coordinators call plays from the coaches' booth.
Kelly said he only called plays from upstairs during his two seasons as Oregon's offensive coordinator. Shurmur, who calls all the plays during the week of practice, watches from above.
"The newest component for me watching Chip call the plays on game day - and I get my practice at it during practice, you know - is the fact that we're basically functioning in a no-huddle setting," said Shurmur, who called plays at two previous stops. "So that part's been fun to learn."
INSIDE THE GAME
Snow and the Cardinals kept the Eagles' screen game in check in the last two games - especially plays set up inside to tight ends and running backs - but Chip Kelly's screens, especially on first down, have been quite effective this season.
There are numerous examples, but LeSean McCoy's 44-yard catch-and-run to open the game against the Buccaneers in October and a 42-yard burst from Brent Celek last month against the Redskins both occurred on first down.
"I think the screen game can be more effective on first and second down," Eagles offensive coordinator Pat Shurmur said. "On third and long, that's obvious. Every defensive guy says, 'Watch the draw, watch the screen.' But in any situation where they're really coming after you with a pass rush, screens can be very effective."
Chris Polk revealed Thursday that he was very close to playing for Chip Kelly at Oregon.
"I was supposed to go to Oregon," Polk said. "If it wasn't Washington, it was Oregon."
Mike Bellotti was the Ducks' coach at the time, but Kelly was the offensive coordinator in 2007 when Polk visited Eugene. But the Redlands, Calif., native ultimately played for Washington.
Since as early as the NFL owners meetings in March, Kelly has included Polk in any discussion when asked about his group of running backs. He always mentions how impressed he was by the workhorse running back when Oregon faced the Huskies.
Polk has drifted under the radar for most of this season playing behind LeSean McCoy and Bryce Brown. But he busted out against the Lions, rushing four times for 50 yards, including a 38-yard touchdown.
Kelly wouldn't say Polk had stolen snaps from Brown, but he did say cite his recent practice performances.
Speaking of bottom-of-the-roster players possibly moving up the depth chart, wide receiver Brad Smith (4) played more offensive snaps than Jeff Maehl (1) and Damaris Johnson (0) against the Lions.
The sample was small, but Kelly has hinted that Smith could become more of a focal point on offense. He did take a snap at quarterback against the Cardinals two weeks ago (and fumbled).
The eight-year veteran has done it all in the NFL. Smith played quarterback in college, but picked up receiver to make himself more attractive to teams around the draft. He doesn't care about titles.
"I'm just a football player first," Smith said, "and whatever I'm asked to do second."
INSIDE THE LOCKER ROOM
Forty-three players from the Eagles' 53-man roster were polled to pick three teammates they would vote into the Pro Bowl. Players were not permitted to vote for themselves (unless the player was Evan Mathis).
Here was the final tally: 1. LeSean McCoy 38 votes, 2. DeMeco Ryans 31, 3. DeSean Jackson 21, 4. Nick Foles 15, 5. Jason Peters 10, 6. Mathis, 6. 7. Jason Kelce 5, 8. Donnie Jones 4, 9. Fletcher Cox 3, 10. Brandon Boykin 3, 11. Riley Cooper 2, 12. Connor Barwin 1.
Cary Williams is the oldest player in the Eagles secondary. He said he has tried to nurture all of the younger defensive backs, but safety Earl Wolff has been a special project for the 29-year-old cornerback. "I guess you could say I gravitate to him because I see his potential, his work ethic and what he puts in," Williams said. "I think he has greatness written on him if he keeps applying himself and plays with passion and fire and with a chip on his shoulder."
BY THE NUMBERS
Number of starts out of possible 286 missed by 22 Eagles starters on offense and defense, using the unofficial depth chart.
Average yards per carry by the Eagles when they run up the middle, which is second in the NFL.
Percentage of run stops (41) from Cedric Thornton per run snap (230), which is first in the league among 3-4 defensive ends. (J.J. Watt of the Texans is second at 14.1.)