The Bears lost 52-21 to the Detroit Lions on Sunday, and while the lopsided outcome didn’t hinge on one play, one play indeed stuck in some Chicago fans’ craws.

With the first half winding down at Ford Field, Lions rookie wide receiver Isaac TeSlaa made an incredible catch along the right sideline and was ruled out of bounds at the Bears’ 4-yard line. That out-of-bounds ruling was overturned upon review, though, as the replay official ruled TeSlaa was in bounds with 16 seconds left and that the clock should have run.

NFL rules dictate a 10-second clock run-off in that situation, giving the Lions one more play with six seconds left. That play resulted in a Jared Goff-to-Amon-Ra St. Brown touchdown pass, and Detroit went to the locker room at halftime with a 28-14 lead.

That odd sequence left Bears fans wondering what they’d just watched, and NFL vice president of instant replay Mark Butterworth provided the following explanation to Detroit News Lions beat writer Nolan Bianchi:

Question: What was initially called on the field and did two officials rule two different things (on the pass from Jared Goff to Isaac TeSlaa late in the second quarter)?

Mark Butterworth: They ruled that it was a completed catch with the receiver out of bounds. The impact of that ruling is the clock stopped because they ruled him out of bounds. If they ruled him in bounds with the catch, the clock would continue to run. We stopped the game through replay to confirm the catch, which we were able to do. We confirmed there was contact by the defense after he controlled the ball, and we had his leg in bounds prior to going out of bounds. Therefore, the clock should have continued to run. So, we reset the clock to the down by contact time and then ran 10 seconds.

Question: How did replay come to that decision?

Butterworth: “We used various angles and were able to confirm he completed the process of the catch. We used two different angles to show that the defender’s right arm did contact the receiver after he controlled the ball.”

Question: When the team with the ball is out of timeouts, is it obligatory to run 10 seconds off the clock after replay?

Butterworth: “Neither team can decline the 10-second run-off, but they can take a team timeout to avoid the 10-second run-off.”