Sproles' offensive production did not decline drastically last season, but he wasn't the return specialist he had been. His history suggests he should upgrade a subpar return game, but his kickoff and punt-return averages last season were almost identical to those of the Eagles' returners.
Kelly places great emphasis on special teams, but Sproles is here mostly because the Eagles coach envisions him as one more toy to tinker with on offense. He's a "little people" plaything - 5-foot-6, 190 pounds - but it's easy to see why Kelly is so enamored.
"He can do it all - run, catch - plus he's a proven winner," Kelly said in a statement. "And, on top of that, he can bring all of those dynamic skills to the return game."
But Sproles has been most effective as a pass catcher, pulling in 378 receptions for 3,381 yards and 27 touchdowns in his first nine seasons. Last season, he caught 71 passes for 604 yards and had the best yards-per-route-run of any running back in the NFL.
Sproles isn't the player he was in 2011, when he had an NFL-record 2,696 all-purpose yards, but he is still one-on-one trouble for defenses.
Kelly took full advantage of running back LeSean McCoy and wide receiver DeSean Jackson's quickness and lateral agility by designing one-on-one matchups.
He likely believes he can devise the same mismatches for Sproles, who is effective in the screen game, can line up in the slot and even split wide. Kelly now has two receiving weapons out of the backfield - McCoy caught 52 passes for 539 yards last season - who will draw defenders from Jackson and other downfield receivers.
Sproles can just as easily motion into the slot or line up there against a linebacker when defenses start using defensive backs to cover tight end Zach Ertz. With receiver Jason Avant gone, Sproles will take some of his snaps inside and provide more yards-after-the-catch capabilities.
As a runner, he should have opportunities to find space in the Eagles' zone-blocking schemes and option plays. Sproles has averaged only 4.1 carries a game over the last six seasons, but at 5.1 yards a tote for his career, he should get enough chances to help trim McCoy's career-high 366 touches last season.
The addition of Sproles doesn't necessarily mean that Bryce Brown or Chris Polk will be jettisoned, but if one were to go, the guess here is that it would be Brown. Brown fell out of favor late in the season after running laterally too often, but he still should have enough value to fetch a mid- to late-round draft pick.
But Sproles will be used more as a receiver - essentially a fourth receiver - behind Jackson, Jeremy Maclin and Riley Cooper, unless the Eagles add more talent. That's a dangerous-looking foursome paired with McCoy, Ertz, and tight end Brent Celek.
How much does Sproles have left in the tank, though? He may not be your typical take-a-beating tailback, but running backs older than 30 (Sproles will turn 31 in June) have a history of taking nosedives. And the significant dip in Sproles' return numbers last season hints at a decline.
In his first eight seasons, Sproles averaged 25.4 yards per kick return and 8.5 yards per punt return. Last season, he averaged 21.3 and 6.7 yards, while the Eagles averages were 21.4 and 6.6 yards.
Sproles had a backbreaking 39-yard kick return late in the Saints' playoff victory over the Eagles in January, but it was his longest of the season.
There's a lot to like about the trade, but was it offensive overkill for a player on the decline, when the Eagles still have holes to fill on defense?