Here's the short version: David Montgomery leaving Detroit is the biggest reason Gibbs is jumping Bijan in some tiers. Let me break it down.
The Montgomery factor. Montgomery was traded to Houston, and Detroit brought in Isiah Pacheco as pure depth — not a direct replacement. Dan Campbell confirmed Gibbs as the "bell cow," targeting 75-80% snap share (up from 67% in 2025). (from the Jahmyr Gibbs page)
The "what if" is already proven. When Montgomery missed games in 2024-2025, Gibbs averaged 32.6 PPR points per contest. At full bell-cow volume (300 carries, ~100 targets), his career averages project to 1,600+ rushing yards, 17-18 TDs, plus 79 catches for 630+ yards. (from the Jahmyr Gibbs page)
Gibbs' receiving role is elite. From Week 11 onward in 2025, he led all RBs in target share (19%), receiving yards per game (48.6), and first-read share — making him a PPR cheat code. Sal Vetri noted that Pacheco is "less versatile" and "not as good from a footwork standpoint" than Montgomery, meaning Gibbs' role is even more secure.
Now, the counterpoint: Bijan still leads the FantasyPros consensus ranks at RB1. He led the NFL with 2,298 scrimmage yards in 2025 and has back-to-back top-3 finishes. The Fantasy Headliners had Gibbs at RB2 in their tier, saying "if you wanted to argue him for number one overall, I wouldn't argue against it."
Bottom line: The 1.01 vs 1.02 debate comes down to Gibbs' newly unlocked ceiling (Montgomery-free) vs Bijan's proven track record. Some rankers lean Gibbs because they'd rather bet on the guy whose path to 300+ touches just opened up, than the guy who already produced 2,298 scrimmage yards and might have minor regression baked in.