The New England Patriots’ decision to trade Jamie Collins was about as shocking as it comes. But it was clear something was up on the first defensive snap of Sunday’s 41-25 win over the Buffalo Bills.

Rookie linebacker Elandon Roberts started the game over Collins and played heavily throughout the game on first and second down, totaling 28 snaps, while Collins uncharacteristically rotated into the game, playing heavily on second and third down for 48 snaps.

There was a method to this madness. NFL teams typically run the ball on early downs and are forced to pass on later downs. Entering the game, opposing offenses were averaging just 3.13 yards per carry when Roberts was on the field and 4.09 yards with Collins on the field. The Patriots let up 6.37 yards per passing play with Collins and 6.99 with Roberts.

The splits were similar in Week 8 against the Bills. The Patriots allowed .23 fewer yards per pass when Collins played and 3.65 fewer yards per carry with Roberts.

Collins was on the field for the Bills’ 28-yard run early in the second quarter and for both rushing touchdowns, one of which was a 26-yarder by quarterback Tyrod Taylor. Collins also was on the field for a running play that went for a 10-yard loss, forced by linebacker Dont’a Hightower and a giant mistake by running back Reggie Bush, who flipped the ball backward in a panic.

Collins, as pointed out by former Patriots executive Michael Lombardi, took an irresponsible angle on the 28-yard run by Mike Gillislee. He tried to make a big play and instead let one up.

Collins shot through his gap, whiffed and slipped, leaving Gillislee to sprint around the left edge for the big gain.

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Collins was run over by Gillislee on the running back’s 3-yard touchdown run. Collins met Gillislee in his gap but couldn’t bring him down.

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Collins also was in the middle of the field for Taylor’s 26-yard scramble TD, though the linebacker probably should have drawn illegal hands to the face, holding and illegal block in the back penalties on the score.

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Roberts, meanwhile, trucked another offensive lineman on the way to tackling a running back just as he did in Week 5 against the Cleveland Browns.

Roberts drove through center Eric Wood and tripped up Gillislee on the same play.

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The Patriots, statistically, are considerably better against the run with Roberts in their defense, while they’re worse regardless of whether Roberts or Collins is in the pass defense.

Collins was better as an individual performer in the passing game, allowing just two catches on two targets for 16 yards, while Roberts allowed three catches on three targets for 36 yards. Collins had two quarterback hits and a hurry while Roberts didn’t generate pressure.

Roberts has allowed eight catches on nine targets for 58 yards with a 94 passer rating against this season, while Collins allowed 18 catches on 24 targets for 128 yards with two interceptions for a 52.1 passer rating for the Patriots. Collins has generated pressure on 16.7 percent of opportunities this season, while Roberts had only one pressure in 19 pass-rush snaps.

So now Roberts presumably will replace Collins on early downs, while players such as Barkevious Mingo and Kyle Van Noy will replace him on later downs.

The Patriots’ decision to trade Collins for at best a 2017 compensatory third-round draft pick when they likely would have received a 2018 third-round comp pick for letting him walk in free agency is a head-scratcher. Even if the Patriots were giving up on Collins as a run defender, they could have used him at the very least as a pass rusher. But Bill Belichick works in mysterious ways.

Other notes from our film review:

— As has become a surprising trend, Patriots right tackle Marcus Cannon was great in pass protection but struggled as a run blocker, while left tackle Nate Solder let up three sacks but played very well in the running game. Up is down, left is right, cats and dogs are getting along, etc.

— Patriots quarterback Tom Brady was 3 of 8 on deep passes. It was his least efficient game throwing deep, but the results still were there. He threw for 124 yards with two touchdowns.

— Devin McCourty showed why he deserves to be considered an elite free safety. He shut down tight end Charles Clay while also taking the top off the Bills’ offense.

— Malcolm Butler and Logan Ryan are up after Week 8, while Eric Rowe, who committed two pass interference penalties, is down. Justin Coleman was so-so. He played well but was flagged for pass interference.

— Hightower was the Patriots’ best pass rusher and made impact plays, including the 10-yard-loss fumble by Bush, but he got caught up on some big plays on the ground. Overall, Hightower was a net positive, but he could improve upon his performance.

— The Patriots didn’t have any dropped passes.

— Running back James White continues to show improvement as a third-down back and still should have a role in the Patriots’ offense when Dion Lewis returns.

— It’s time to mention James Develin has not been good this season. The Patriots fullback keeps being overpowered.

Thumbnail photo via Timothy T. Ludwig/USA TODAY Sports Images