SANTA CLARA, Calif. -- Considering just how well his own quarterback has played over the past three weeks, Jacksonville Jaguars coach Doug Marrone's glowing evaluation of San Francisco 49ers quarterback Jimmy Garoppolo came as something of a surprise when Marrone was speaking to Bay Area media Wednesday morning.

"He’s as good as it gets right now for what’s going on around the league," Marrone said.

To be sure, Marrone's praise sounded sincere, as opposed to some of the respect-your-opponent platitudes that often come from such media sessions. Make no mistake, Marrone should know greatness when he sees it, because he's going to arrive for Sunday's game at Levi's Stadium with perhaps the ultimate counter to Garoppolo's recent run of success: the league's most dominant defense.

“I look forward to it a lot, for our whole team," Niners coach Kyle Shanahan said. "I do believe that they have as much qualities as anyone that it takes to win a Super Bowl: a top defense, a very good running game, a good offense, good special teams. When you see a team like that on tape that you believe has that ability, it’s a good thing, it’s a good challenge for your team to go against them and see where you’re at.”

For Garoppolo, who according to Elias Sports Bureau became the first quarterback in NFL history to win each of his first three starts for a team while passing for 1,000 or more yards in those games, it's the best test yet of just how far he's come since the Niners finalized the trade for him on Halloween.

Of course, Garoppolo and the Niners have heard some variation of that for each of the past three weeks. After beating Chicago, it was "Yeah, but how will he do against Houston?" After beating Houston, it was "Yeah, but what will happen against a playoff team like Tennessee?" And after Garoppolo passed those tests, the skeptics circled this week's game as the ultimate trial for the quarterback and the surging Niners offense.

While this game shouldn't be viewed as some sort of referendum on Garoppolo's place in the NFL quarterback hierarchy -- more proven quarterbacks have taken unpleasant trips to "Sacksonville" -- it would send quite a message if he is able to play well and lead the 49ers to their fourth consecutive victory.

“It’ll be good," Garoppolo said. "It’s a great challenge for us on Sunday. Like I said, though, every week -- we just went against a great defense in Tennessee. Every week is another challenge and a different type of challenge. We have to change our mindset and thinking of how we attack this defense compared to that defense and go about our week like we did these last couple and have a good week of practice.”

So, what exactly do the Niners have to deal with in Jacksonville's defense? For starters, it's a unit that features four Pro Bowlers in cornerbacks A.J. Bouye and Jalen Ramsey, defensive end Calais Campbell and defensive tackle Malik Jackson. That doesn't even account for those who were snubbed, like end Yannick Ngakoue and linebacker Telvin Smith.

With talent like that leading the charge, Jacksonville's defense ranks first in the NFL in scoring defense (14.9), passing yards allowed per game (168.9), completion percentage allowed (56 percent), sacks (51) and total QBR allowed (38). The Jaguars are second in takeaways (31), interceptions (20) and rushing touchdowns allowed (six) and third in yards allowed (284.1).

Schematically, Jacksonville operates out of a system very similar to what the Niners run, which should at least allow Garoppolo to get a good look at what he'll see on Sunday from an X's and O's standpoint. But the key to the Jaguars' success is the ability of their front four to get after quarterbacks without the need to bring additional pass-rushers.

After last week's win against the Titans, Shanahan and left tackle Joe Staley said they saw more blitzes than they ever had in their careers. That isn't likely to happen again this week, as Jacksonville has brought five or more rushers just 93 times this year, the fewest in the league and well short of the league average of 147.6.

That allows the Jaguars to drop more defenders into coverage while still generating pressure, a combination few teams possess and one Garoppolo had yet to see as San Francisco's starter.

“It’s a lot different because there’s not as many holes in the defense," Shanahan said. "Every time you blitz, it leaves a hole somewhere. When you don’t blitz, sometimes you’ve got to wait on those holes to get open longer. And any time you’re No. 1 in the league in sacks and hitting the quarterback, it shows that you can get to the quarterback with four. And that allows you to play much more sound, aggressive coverage.”

As you might expect, given how unflappable Garoppolo has been in his three starts, he's doing his best to not look at the Jaguars as different from other opponents. Asked Wednesday how he viewed his long-term future with the Niners, Garoppolo made it clear he didn't want to look past Sunday's game.

“If we handle the Jaguars well, that’ll be a good test for us. And [if we] finish out the season well, we’ll figure it out after that,” Garoppolo said.

Logic dictates that Garoppolo and the Niners aren't going to win every game. And for as good as Garoppolo has been, he's going to face adversity at some point. That point could be Sunday, when Campbell and Ngakoue are closing in on him and Ramsey and Bouye are sticking to his receivers like glue.

Even if Garoppolo struggles, it would offer another prime opportunity for Shanahan, the Niners and their faithful to understand just what they have in their new franchise quarterback.

"There's going to be a time that he goes through adversity," Shanahan said. "I'm sure some day he will lose and guys have rough games. I don't care how good you are or if you're the greatest quarterback of all time. I've heard people over the years, whatever the two or three games that [Patriots QB] Tom [Brady] has had that haven't been very good, usually the next day people are saying, all right, he might be getting older, and then he usually finishes the year with an MVP and a Super Bowl trophy. In order to see how guys are doing, you've got to see how they respond to adversity and how they can do it over the long haul. Jimmy is going to get that opportunity and we'll see, and I feel pretty confident he'll handle it the right way.”