Shanahan explains why Purdy hesitated on potential Aiyuk TD vs. Rams originally appeared on NBC Sports Bay Area

The Los Angeles Rams’ defense gave the 49ers a major opportunity to put Sunday’s game away with a breakdown in the defensive backfield.

But the Rams’ mixup was so extreme that it even caught the 49ers by surprise.

To the untrained eye, it looked as if 49ers quarterback Brock Purdy made a major mistake in not seeing Brandon Aiyuk wide open for a potential touchdown late in San Francisco’s 27-24 loss to Los Angeles.

But, according to coach Kyle Shanahan, it actually was a huge error by the Rams’ defensive backfield that caused enough confusion for Purdy to hold onto the football a split-second too long.

Leading 24-17 with approximately four minutes remaining in the fourth quarter, the 49ers had a first-and-20 situation at their own 48.

On the play, Aiyuk was open as he ran down the field. Purdy saw Aiyuk but did not let it fly.

So what happened?

Aiyuk changed his route because he recognized the Rams’ mistake. Purdy saw Aiyuk, but he had to process whether there was a safety lurking in the vicinity.

Purdy ended up holding onto the ball, scrambling back to his right and throwing a pass to Jauan Jennings for a 5-yard gain.

“B.A. had a deep curl route and they busted a coverage, so B.A. did the right thing and took off and went to that hole,” Shanahan explained Monday on a conference call with Bay Area reporters.

“It kind of caught Brock by surprise because B.A. was No. 2 in the progression. When he looked to him, he wasn’t in the right spot because they busted a coverage.”

When Aiyuk continued down the field in hopes of taking advantage of the Rams’ defensive error, it caused uncertainty for Purdy, Shanahan said.

Shanahan explained that in the coverage the 49ers recognized, the corner on Aiyuk’s side should have played the deep half of the field. Instead, the corner played the shallow route and the Rams did not have a safety over the top to play the deep ball on that side.

“He wasn’t anticipating that to happen,” Shanahan said of Purdy. “It would’ve worked, obviously, if he let it go, but that happens sometimes. The defense busts a coverage and if you’re not looking at the guy the whole time, all of a sudden it turns into a go-route and you can’t always just let it rip.”

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