If a team wants to make its ordinary quarterback look outstanding, all it has to do is pressure the daylights out of his counterpart.

Cooper Rush of the Dallas Cowboys is an ordinary-at-best quarterback who has spent his five N.F.L. seasons as a barely used backup. Yet this season, Rush has led the Cowboys to four straight victories in relief of Dak Prescott.

He has done so in large part because the Cowboys pass rush of Micah Parsons, DeMarcus Lawrence, Dorance Armstrong and Dante Fowler Jr. has sacked opposing quarterbacks 20 times for 128 yards, and the Cowboys defense has held opponents to just 14.4 points per game.

Jimmy Garoppolo has been the chairman of the Ordinary Quarterback Society for so long that the San Francisco 49ers unfriended him in favor of Trey Lance in the off-season. Garoppolo has led the 49ers, now 3-2 and in first place in the N.F.C. West, to three lopsided victories in four games since replacing the injured Lance, thanks in large part to a Nick Bosa-led defense which leads the N.F.L. with 21 sacks and 142 sack yards, holding opponents to just 12.2 points per game.

It never fails: Defenders do most of the dirty work; quarterbacks get the attention. Rush and Prescott, set to soon return from a thumb injury to his throwing hand, are now embroiled in a rather contrived controversy. Some 49ers fans are now convinced that trying to replace Garoppolo with Lance was always a bad idea.

Quarterbacks like Rush and Garoppolo are often credited with “finding a way to win” games in which their opponents were busy finding ways to escape.

Quarterback drama keeps the sports-media industrial complex humming, of course, and “Bench Dak” makes a splashier headline or podcast title than “Micah Parsons is Good.” There’s another dynamic at work, however: A great defense really does make its quarterback look better.

Garoppolo and Rush, currently ranked seventh and 12th in passer rating and fourth and tenth in Football Outsiders’ rankings for Defense-adjusted Value Over Average, are benefiting from a powerful statistical distortion.

On average, N.F.L. quarterbacks attempt 52 percent of their passes while trailing, 30 percent when leading and the remaining 18 percent with the score tied, with sacks counted among the pass attempts. The reason for the disparity should be obvious: Teams pass more and take greater risks when playing catch up than they do when nursing a lead.

All of those extra risks — against defenses that know what’s coming — mean that quarterbacks complete a lower percentage of their passes (63.0 percent to 65.7), average fewer yards per attempt (7.0 to 7.7), throw interceptions at a higher rate (2.8 percent to 1.6) and get sacked at a higher rate (7.0 percent to 5.4) when trailing than leading.

To summarize for readers whose eyes glazed over at the sight of all those decimals: Ordinary quarterbacks are likely to produce Pro Bowl-level statistics when leading and put up bench-the-bum statistics when trailing, simply owing to the tactics used in different game situations.

Quarterbacks usually attempt many more passes when trailing than leading. A stingy, turnover-happy defense can make matters even easier for an ordinary quarterback, giving him the benefit of playing with leads he did little to generate and leaving him to finish out games with efficient, high-percentage passes.

Take the Cowboys victory against the Los Angeles Rams in Week 5, for example. Armstrong forced a Matthew Stafford fumble which Lawrence returned for a touchdown on the opening drive, then blocked a punt to set up a short Cowboys field goal. The Cowboys led, 9-0, before Rush completed a single pass, and he played with a lead most of the way to a 22-10 victory.

Rush has attempted just 26 passes with the Cowboys trailing this season, 57 while leading. That’s practically the inverse of the typical N.F.L. ratio. It’s easy for a quarterback to go four games without an interception when he spends most fourth quarters handing off.

Garoppolo’s splits are even more revealing: He has thrown just 11 passes with the 49ers trailing, 85 while leading. The 49ers defense returned an interception for a touchdown and forced Carolina Panthers quarterback Baker Mayfield to hobble through their 37-15 victory last Sunday on a sprained ankle. Garoppolo, who has thrown only one interception this season, was free to spend another afternoon distributing micro-passes, handing off and watching the clock melt away.

A team’s vicious pass rush has other hidden benefits which go beyond sack totals. The Cowboys have coaxed a league-high 11 false starts from opposing linemen hoping to get a jump on blocking Parsons and company, as well as two intentional grounding penalties when Washington Commanders quarterback Carson Wentz desperately heaved passes away to avoid being sacked in Week 4.

The 49ers defense forces opponents to go three-and-out on 39.6 percent of their possessions, the highest total in the league according to Football Outsiders, providing their offense with more possessions.

Constant pressure has a snowball effect: Sacks and turnovers force the opponent to play from behind, which means they must take greater risks, which lead to more mistakes and an ever-widening deficit. Under the right circumstances, a victorious “game manager” barely breaks a sweat.

Fortunately, quarterbacks don’t get all the credit. Parsons is now the even-odds favorite to win the Defensive Player of the Year award. Bosa is one of the league’s most recognizable stars. Rush will most likely be forgotten by everyone but the dedicated drama junkies upon Prescott’s return, and Garoppolo long ago galvanized his reputation for helping the 49ers by doing minimal harm.

If the Cowboys and 49ers keep sacking their way toward the playoffs, their defenders are sure to get their due.

An excellent pass rush can even lead a team with an ordinary quarterback to victory in the Super Bowl. Who can forget the legendary teams led by famously less-than-stellar passers like Trent Dilfer, Joe Flacco, Mark Rypien, Jim McMahon or, let’s be totally honest, Eli Manning?

Wait, why do we remember those quarterbacks so readily when we are supposed to be praising their defenses?

Sigh. Even when a defense leads its team to a championship, it’s the quarterback who somehow secures a place in history.