DeSean Jackson may seem like a pedestrian NFL wide receiver — very talented but far from spectacular in an era when wideouts regularly post 100-catch campaigns. Since he came into the NFL in 2008, Jackson is 17th overall in receptions and 15th in touchdown catches.

But Jackson, now with Philadelphia, has led the NFL four times in yards per receptions, including last year for the Buccaneers at age 32. That’s more than any other player in NFL history. And his electrifying speed seems to dramatically enhance his team’s overall passing game. Having Jackson in uniform has boosted the yards per pass play of his teams. And when he’s gone, his former teams have quickly lost these games. That bad news for Tampa Bay, Jackson’s team last year, which had the 23rd best season in the statistic since the 1970 AFL-NFL merger.

Jackson’s newest quarterback noticed quickly that Jackson’s ability to take the top off the defense by getting behind the secondary makes the rest of the field easier to attack. Defenses have no choice but to play deeper.

“(This) takes pressure off all the other guys,” Carson Wentz said. “He’ll open up a lot of things underneath, we truly believe. … He just threatens defenders in a different way.”

Still, teams seem to have a hard time reconciling Jackson’s team value with his often underwhelming personal statistics. Since he broke into the league, he’s been on four squads, if you count his two stints with Philadelphia.

Jackson’s nomadic career makes it easier to quantify his impact. This effect can be seen at the team level when looking at how they perform during Jackson’s stay there compared with before as well as immediately after he leaves.

DeSean Jackson makes the offense better Net yards gained per team passing attempt for DeSean Jackson’s teams, by when he was on the team Yards per pass by when Jackson joined the team Team Years Year before First year Last year Year after Philadelphia 2008-13 6 6.2 7.4 6.7 Washington 2014-16 5.7 6.7 7.6 6.5 Tampa Bay 2017-18 6.4 6.8 7.7 ? Net yards per pass attempt counts sacks as pass plays and subtracts those yards from the total passing yards. Source: Pro-Football-Reference.com

The numbers in Jackson’s last year with his teams are especially noteworthy. Among all teams since 1970 — that’s out of 1,445 team seasons in the period — they rank 57th (2013 Philadelphia), 32nd (2016 Washington) and 23rd (2018 Tampa Bay) in yards per pass play. This means each one finished in the 95th percentile or better.

Each of Jackson’s teams immediately gained in passing efficiency once he arrived. And both Philadelphia and Washington significantly declined once he left, by nearly 1 yard net per pass play. To put that into context, ranking last year’s teams by that measure, just 0.9 net yards per attempt separated the ninth-ranked Colts (6.7) and the 25th-ranked Lions (5.8). Those teams were 10-6 and 6-10, respectively, which is not surprising given that teams that win the yards-per-pass-play stat by any margin have won about 74 percent of games since the merger, according to my reporting for The Wall Street Journal.

Of course, it’s possible that these teams became more prolific at passing coincidentally upon Jackson’s arrival, via coaching, play-calling, quarterback performance or the skills of the team’s other receivers. Jackson has struggled with durability during his career, missing nine games in his first stint with the Eagles, eight with Washington and six with the Buccaneers. So if there is a significant Jackson effect, it should be apparent when looking at his team’s performance when he plays versus when he’s inactive. And it is:

The splits on Jackson’s teams when he’s on and off the field Stat Without With Pass attempts 861 5,478 Pass yards 5,535 40,772 Net yards/pass play 5.63 6.56 Source: Pro-Football-Reference.com

Jackson’s active-and-inactive effect is even more pronounced than the difference before and after he joined his teams, at 1.03 yards per pass play.

Not surprisingly, given the impact of yards per pass play on wins and losses, Jackson’s teams with him inactive are 8-15 (.348 win percentage) compared with 75-76-2 (.497) when he plays.

It’s also possible that the effect Jackson seems to be creating for his team is really just a result of his own efficiency. After all, he’s averaged 9.7 yards on the 1,057 passes he’s been thrown in his career, counting incompletions.

But last year, Jackson’s ability to threaten defenses deep did seem to significantly benefit his team’s primary receiver. Mike Evans averaged a career-best 11.0 yards every time a pass was thrown his way, a startling 2.4 yards greater than his prior season high (in 2014). And Evans was thrown the ball 138 times, nearly twice as frequently as Jackson (74 targets). For Washington, Jackson’s tight end teammate Vernon Davis (2016) boosted his yards per target by over 3.0 yards from the prior year. And another Washington tight end, Jordan Reed, averaged 7.8 yards per target with Jackson from 2014 to 2016 and since has dropped to just 6.5. During Jackson’s last stint in Philly, Riley Cooper averaged 9.9 yards per target, 10th-best in the league that year. But the next year, without Jackson, that collapsed to 6.1. Cooper has been out of the NFL since 2015.

The question now is whetherJackson can be expected to maintain his fleet feet entering his age-33 season. The Eagles sure seem to think so, awarding him a three-year, $27.9 million contract this offseason with more than half the money guaranteed.

Jackson’s 18.9 yards per catch in his age-32 season was third-most since the merger (minimum 40 catches). The average age-33 season of the other seven receivers with more than 17.0 yards at age 32 was 53 catches for 769 yards. Two of them, Irving Fryar and Frank Lewis, subsequently made the Pro Bowl. Another, Steve Smith, had two 1,000-yard seasons. But unlike Jackson, none of these other seven receivers led the NFL in yards per reception even once, never mind a record-setting four times.

While there’s no way to know for certain the player the Eagles have, there’s little question about what Jackson has been so far in his career.