The Eagles would certainly take a repeat of Jackson's 2013 (82 catches for 1,332 yards and nine touchdowns), but Kelly doesn't really need for Maclin to put up those numbers on his own for the offense to keep humming. A handful of candidates can duplicate those numbers by committee.
Maclin just needs to be who he was before he tore the anterior cruciate ligament in his right knee - 70 catches, 900 yards, and eight touchdowns would do. Are those the kind of statistics that will garner him the No. 1-receiver contract he seems intent on earning this offseason? Probably not.
But at this point, it probably would exceed expectations for a player one year removed from the second ACL injury of his career. Maclin has cleared various hurdles since making a full return in the spring, but the most significant to date comes Friday in the preseason opener at Chicago.
That is, if Maclin plays. He didn't participate in team drills during the Eagles' last two practices in pads this week. He said that "soreness" in both legs limited his participation but that he could have played if necessary and that he would be ready for the Bears.
On Wednesday, Kelly said he wasn't sure about Maclin's availability. It would be preferable if he played once before the season opener - Maclin hasn't played in a competitive game since Dec. 30, 2012 - but the feeling here is that the Eagles are trying to get to Sept. 7 without any major setbacks.
"It's different because I had ACL surgery," Maclin said when explaining why he watched most of Tuesday's session. "I guess it's just protocol."
Maclin's first torn ACL occurred before his freshman season at Missouri and he redshirted for a year. In his first four seasons with the Eagles, Maclin missed four games and failed to finish three others because of injury.
The "not-tough-enough" tag has dogged him since he came to the NFL. He didn't seem to be able to return kicks or punts, even though he was prolific at both in college. And he has occasionally taken post-catch detours out of bounds or to the ground.
But he has also bounced back from big hits. In 2011, only weeks after doctors cleared him after a lymphoma scare and he missed all of the preseason, Maclin had the best game of his career. He caught 13 passes for 171 yards and two touchdowns and endured a helmet-to-helmet blow from Dunta Robinson in a loss to Atlanta.
Maclin's naysayers, though, would point to the fourth-down, over-the-middle pass he dropped that ended the Eagles' comeback hopes in that game.
That is the paradox of Maclin.
"He's good at most things - a good route runner, good run after the catch, good speed and quickness," a senior NFL scout said. "But he's not really good at anything. He struggles vs. press coverage, reading rotating coverages, and he's not the toughest guy."
Kelly's opinion differs, obviously, or he wouldn't have re-signed Maclin to a one-year, $6 million contract in the offseason. The Eagles tried to get him to sign a multiyear deal that did not include the guaranteed money that topflight receivers typically get. (Jackson received $16 million from the Redskins.)
Maclin bet on himself, though, and this season. There are plenty of reasons to think the former first-round draft pick could pop in his fifth season of playing.
"He's explosive, he gets off the line of scrimmage. He obviously has speed to separate. He's a very, very good route runner," Kelly said. "He's got some legitimate line-of-scrimmage strength where he can kind of maneuver a little bit, doesn't get knocked off balance.
"He catches the ball really well, and . . . you've seen it before with him on film . . . he's really good with the ball in his hands after the catch."
Maclin's career yards-after-catch average, though, is only 4.2 per reception. Jackson, by comparison, has averaged 5.7 and was only slightly above his average last season (5.9).
Maclin doesn't have Jackson's speed, but he's as efficient catching deep balls (passes over 20 yards). In the four seasons they played together, Jackson was targeted more but caught only seven more passes and two more touchdowns.
He had more than 500 yards than Maclin on deep balls, but that was Jackson's role. Maclin did a lot of the dirty work underneath. He should have more opportunities to blow the lid off a defense. It should be noted that Riley Cooper averaged 17.8 yards per catch last year, third in the NFL.
Downfield blocking is a big part of Kelly's offense, so Maclin will have to be more consistent in that regard. He has taken exception to criticism before, firing back at a blogger this summer who questioned his effort and suggested he was merely average.
The best way he can answer his critics is to perform. It's that simple. He has a great opportunity.