The San Francisco 49ers are indiscriminate in how they go about terrorizing defenses.

They have a star running back, Christian McCaffrey, who lines up out wide and a star fullback, Kyle Juszczyk, who shows up in the slot. They have a star tight end, George Kittle, who can block like a sixth lineman. They have a star wide receiver, Deebo Samuel, who takes carries out of the backfield. They have another star wide receiver, Brandon Aiyuk, who’s one of the NFL’s best route runners. They have a star quarterback, Brock Purdy, who trusts his playmakers to win in space. And in coach Kyle Shanahan, they have an offensive mastermind tying everything together.

“They do so many good things,” Ravens coach John Harbaugh said Monday of San Francisco’s top-ranked offense, which ranks first in passing efficiency and third in rushing efficiency, according to FTN. Shanahan “really has expanded it and evolved it in a great way, and he does it around his players, too. … I mean, you’ve got five, probably, All-Pro skill guys on that offense and, not to mention, a really good offensive line and a Hall of Fame tackle [Trent Williams]. So he’s built it around those guys, and that’s what makes it tough.”

As the AFC-leading Ravens prepare for their Christmas Day showdown with the NFC-leading 49ers, no unit will be more important in coordinator Mike Macdonald’s scheme than his second-level defenders. With its relentless presnap motion, unique play design and elevated skill level, San Francisco’s offense puts undue stress on off-ball linebackers and slot defenders. In Roquan Smith and Patrick Queen, the Ravens have one of the NFL’s best linebacker duos. In Kyle Hamilton, they have one of the NFL’s best box safeties.

Here’s a look at how the 49ers attack defenses — and how the Ravens could stop them.

Diagnose and react to presnap motion

Entering Week 14, according to ESPN, the 49ers had used presnap motion on 76.2% of their plays, the NFL’s second-highest rate, and had put a player in motion at the snap on 36.9% of their plays, the league’s third-highest rate.

Just as notable as the volume on Shanahan’s motion menu is the variety. San Francisco will send McCaffrey down one sideline on an “exit motion,” the Miami Dolphins-inspired look that gives receivers a running start at the line of scrimmage.

Or the 49ers will send Samuel into the flat on a “orbit return motion,” in which a receiver motions behind the deepest back in the backfield.

Or they’ll send McCaffrey on a short motion that creates new angles for him out of the backfield.

On plays with presnap motion this season, Purdy is second in the NFL among qualifying quarterbacks in passing yards (2,719), fourth in completion percentage (70.3%) and first in expected points added per drop-back (0.27), according to the NFL’s Next Gen Stats.

The Ravens, who pride themselves on their “obnoxious” presnap communication, led by Smith, should be one of Purdy’s stiffest tests yet. Against passing plays with presnap motion this season, the Ravens rank tied for second in yards allowed per attempt (5.9), fourth in sack rate (8.5%) and first in EPA per drop-back allowed (minus-0.23).

Their past two weeks have been a struggle, though. The Los Angeles Rams’ Matthew Stafford and Jacksonville Jaguars’ Trevor Lawrence combined to go 12-for-15 for 160 yards and a touchdown against the Ravens with the help of motion, averaging an elite 0.71 EPA per drop-back. Lawrence’s 65-yard touchdown pass Sunday to wide receiver Jamal Agnew came after a motion out wide led to an apparent coverage bust downfield.

Finish tackles on screen passes

The Kansas City Chiefs’ Patrick Mahomes leads the NFL with 496 passing yards on screens this season, according to NGS. And yet, as measured by EPA per drop-back (0.20), he hasn’t been even half as efficient a screen thrower as Purdy this season (0.44).

Overall, Purdy is 33-for-36 for 379 yards and three touchdowns, tearing defenses apart with an egalitarian approach. 49ers running backs have 157 receiving yards on screen passes this season; their wide receivers have 195; and their tight ends, 27.

San Francisco’s screens weaponize the open-field ability of its skill position players. Kittle is a pain to bring down. McCaffrey is among the NFL’s most elusive backs. And Samuel is a nightmare after the catch, especially when Williams is clearing a path for him.

The Ravens have faced the third-most passes behind the line of scrimmage in the NFL this season (109), according to NGS, but they rank third in success rate. Opposing quarterbacks are averaging just 4.1 yards per attempt (tied for fifth best) and minus-0.32 EPA per drop-back (ninth best) on those short passes.

Leading the way are Smith and Queen, whose sideline-to-sideline speed helps erase promising paths for ball carriers, and Hamilton, who’s been nearly unblockable in the slot.

React to zone runs and play-action passes

The 49ers do not rely exclusively on zone concepts in their running game, but they do major in them. About two-thirds of San Francisco’s carries this season have been zone runs, in which blockers move in tandem to block an area rather than a man.

According to Sports Info Solutions, McCaffrey has rushed 165 times for 857 yards (5.2 per carry) and 10 touchdowns on zone concepts this season. With the eye candy that the 49ers show defenses before the snap, and the wall-off blocks that Juszczyk and Kittle can deliver after it, the gap integrity of the Ravens’ off-ball defenders will be tested regularly next week.

Still, their run defense has largely fared well against zone schemes this season. Opponents have racked up just 772 yards (4.2 per carry) and minus-0.13 EPA per rush attempt. Take away Tennessee Titans running back Derrick Henry’s 64-yard run on a Wildcat snap in London, and the Ravens have allowed just 3.9 yards per zone carry.

McCaffrey’s breakaway potential as a runner — he has eight carries of at least 20 yards this season — makes San Francisco’s play-action attack all the more potent. On run fakes, Purdy is 63-for-82 for 848 yards, 11 touchdowns and one interception this season, according to NGS. Among qualifying quarterbacks, he’s first in both EPA per drop-back (0.41) and success rate (61.3%) on play-action passes.

Despite the Ravens’ up-and-down run defense, they’ve seldom been burned by play-action. The defense has given up as many touchdowns as it has recorded interceptions (one), and it ranks third in EPA per drop-back allowed and fifth in success rate. When the Ravens faced the Rams in Week 14 — an offense that shares some DNA with the 49ers’ — Stafford went just 3-for-9 for 52 yards on play-action drop-backs.

Opponents have also generally avoided the zones that Smith, Queen and Hamilton retreat to on play-action passes. The Ravens have faced just 12 such short and intermediate throws over the middle third of the field, according to NGS, tied for the fourth fewest in the league.

Cover throws to McCaffrey

McCaffrey leads all NFL running backs in receiving yards (509) and touchdowns (seven), and his role in the 49ers’ screen game explains only part of that success. McCaffrey also leads all running backs in targets (50) and catches (40) at or past the line of scrimmage, as well as receiving yards (374) and touchdowns (five) on those attempts.

McCaffrey’s route-running ability affords the 49ers rare positional flexibility. According to SIS, he’s run 77 routes from the slot this season, recording 15 catches for 153 yards and two touchdowns, and run another 25 routes out wide, making seven catches for 71 yards.

On paper, the Ravens match up well athletically with McCaffrey. But their coverage of running backs on passes downfield has been spotty this season. According to NGS, on throws past the line of scrimmage, the Ravens have allowed 7.3 yards per attempt (10th most).

They’ve given up a handful of explosive plays, too. Hamilton’s overaggressiveness led to a long catch-and-run by the Cincinnati Bengals in Week 2. Queen gave up a jump-ball touchdown to the Indianapolis Colts a week later. And an apparent miscommunication on coverage distributions hurt the Ravens against the Detroit Lions in Week 7.