There are a few repercussions here from a fantasy football standpoint. To put it simply, it's a clear upgrade for Ajayi's fantasy stock despite a potential volume decrease.
The Dolphins currently rank as second-from-last in the NFL in rushing offense, averaging a mere 76.4 rush yards per game and a combined 3.2 yards per carry average. Miami remains the only team in the NFL without a rushing touchdown this season. Football Outsiders currently has Miami's o-line as the 28th-ranked run-blocking unit of 2017.
Ajayi now lands in a Philadelphia backfield that ranks fifth in the NFL in rushing, averaging 129.2 rush yards per game on the heels of 30-plus rush attempts per contest. From an overall offensive production standpoint, Miami is currently dead-last in the NFL averaging a mere 13.1 points per game compared to Philadelphia's 29 offensive points per game, fifth in the league.
Yes, there are other players in the Eagles backfield that could muddle Ajayi's situation temporarily, but the move signals that Philadelphia was not content to move forward with a rotation of the one-dimensional LeGarrette Blount and change-of-pace second-year player Wendell Smallwood. Ajayi brings a three-down skill set to the Eagles backfield, something a team with the best record in the NFL at 7-1 lacked. And despite a narrative that has seemingly stuck with Ajayi throughout his career, he does have pass-catching abilities. He caught 50 passes in his final college season at Boise State and last year as Miami's feature back he logged 27 receptions for 151 receiving yards. The Eagles can and will use him as a feature back on all three downs.
Ajayi's arrival in Philadelphia means a huge reduction in fantasy value for Blount, Smallwood and any value Corey Clement had (which wasn't much). Once the 2016 Pro Bowler gets acquainted with his new offense, Ajayi will take over as the primary option there. He succeeded in a featured role last season and finished as fantasy's RB11 in standard scoring with over 1,400 yards from scrimmage and nine total touchdowns on a 287-touch workload. His 2016 campaign included three 200-yard rush games.
Something to keep in mind is Ajayi's schedule for the rest of the season with the Eagles. They get the Broncos, who are allowing the fewest fantasy points per game to running backs, at home in Week 9 followed by a Week 10 bye. The matchups following (and FPPG allowed to RB rank) include the Cowboys (16th), Bears (14th), Seahawks (seventh), Rams (31st), Giants (15th) and Raiders (26th) through Week 16. Fantasy owners can consider Ajayi a starter in all of those matchups.
In Miami, the running backs left on the roster include Kenyan Drake, Damien Williams and Senorise Perry. Drake is a 6-foot-1, 210-pound Alabama product that coach Adam Gase selected in the third round of the 2016 NFL Draft and is the favorite to take over the primary role in the Dolphins' backfield. Drake's skill set includes 4.45-40 speed and a solid athletic profile in terms of explosiveness and agility. Drake was the only other back who got work behind Ajayi in Miami's Week 8 blowout loss to the Ravens. Williams is a fourth-round player who saw some work last season in goal-line situations, totaling six touchdowns on the season and playing the role of Ajayi's touchdown vulture on more occasions than fantasy owners would have liked. There's a good chance we see a rotation between these to players going forward.
In a stretch of the season where the waiver wire is thinning out, especially at the running back position, Ajayi's departure from Miami creates a few names for fantasy football managers to chase ahead of Week 9. But keep expectations reasonable and keep in mind the state of Miami's offense -- it's not great.