The San Francisco 49ers will have a pivotal test right out of the gate in Week 1 of the upcoming season, as they are set to square off with the Justin Fields-led Chicago Bears offense.

49ers defensive coordinator DeMeco Ryans game planned against Fields last season, and his defense had mixed results. While the 49ers came away with a double-digit victory and also held Fields to under 200 passing yards in the Week 8 matchup, the former Ohio State standout proved to be too much for their front seven on the ground; he tallied a career-high 103 rushing yards and also scored one rushing touchdown.

As Ryans continues to prepare his defense for the task of containing Fields, he is much wary of what the versatile quarterback can produce on the ground.

“I mean he’s a tremendous athlete, right?” Ryans said during a press conference ahead of the 49ers’ Week 1 opener against the Bears. “He got out on us last year a lot, made a lot of big time plays, big time runs that normal quarterbacks can’t make so the guy is very athletic, he can run all over the place.

“So, we have to, as we rush and as we play our coverages, we have to be very aware of that. Because of the type of athlete that he is, the speed that he has he can get out on you and make you pay so we just have to be conscious of that and be disciplined in everything that we’re doing. … When you’re rushing this guy, you just have to be aware of who are you playing, right? We’re not playing a quarterback who’s just going to sit in the pocket and just take a sack, that’s not who he is. This quarterback, he’s a mobile quarterback, he’s athletic, he can get out on the edge, he can get out through the middle, that’s who we’re playing.”

The 49ers do head into this contest with a few minor injury concerns, but at the least, the likes of Nick Bosa and Fred Warner will be available to help slow down the Bears’ new-look offense in Week 1.