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Brock Purdy made an emergency relief appearance for the injured Jimmy Garoppolo and was essentially a clone of Garoppolo in the 49ers' win over the Dolphins

This was a seventh-round rookie, Mr. Irrelevant from April's draft, who played calm, cool, and collected after being thrust onto the field for his first meaningful NFL action in the thick of a colossal showdown against a red-hot Miami team.

Hats off to Purdy for a tremendous display of confidence in such a challenging spot. And, my word, as if he hasn't provided enough evidence to date, what a testament it was to the brilliance of Kyle Shanahan's scheme and play calling. Oh, and can't forget the embarrassment of riches San Francisco has on offense. While on the surface, it was costly victory for the 49ers, the 33-17 win against Mike McDaniel's club showcased the completeness of Shanahan's squadron. 

Check the genius of the play design here from Shanahan. Trips formation to the bottom of the screen. McCaffrey motioned, leaving a stacked look. Every time a secondary gets that pre-snap alignment, one of the corners will play off, to avoid easily getting picked. That space left plenty of room for Jauan Jennings to run behind Brandon Aiyuk for a few yards before breaking to toward the sideline. Schemed open throw for Purdy. First down, San Francisco. 

Easy pitch and catch. But what do the 49ers have in Purdy, and can he help navigate this team through the playoffs and to the Super Bowl

Let's start with Purdy the prospect. Even if you didn't catch a second of the 49ers' Week 13 victory, but knew he was the final pick in the draft, you'd likely guess Purdy is not a freaky physical specimen, and you'd be right. He's slightly under 6-foot-1 and 215-ish with an average-at-its-very-best arm. 

And here's an example of his arm-strength limitations. Purdy goes next-level at the outset of this play -- foreshadowing! -- by looking to left to draw the safety away from the backside post to Deebo Samuel. And it was there. But notice the lack of velocity on the football, which allowed the pass breakup to be made. 

How about positives? What does Purdy do well? Here are those snippets from my pre-draft scouting report.

"Surprising athletic twitch... will elude some defenders with his change-of-direction ability... shows good pocket movement skills... anticipatory throwing skill masks some of his arm-strength deficiencies."

And we saw many of those positives in the win over Miami. Don't believe me on the athleticism part? Here's some evidence. 

Like I wrote "surprising athletic twitch," right?! Love the little sidearm sling too. 

Shanahan demonstrated immense faith in Purdy in this game. That's telling. The rookie dropped back to pass 40 times (!) on Sunday and was 25 of 37 (67.5%) for 210 yards with two touchdowns and an interception. Isn't that a Jimmy G stat line? Darn close. 

Digging deeper, 59.4% of Purdy's attempts were either behind the line of scrimmage or up to five yards beyond it. Seems high, right?

Well, actually no. Not really. Shanahan -- and his QB -- stayed true to the team's pass-game philosophy. Before his injury, 54.5% of Garoppolo's throws this season were either behind the line or up to five yards beyond it. 

In essence, Shanahan didn't tweak the offense once Purdy entered, and the rookie quarterback was ready to play like the veteran he replaced. Amazing, really. 

Speaking of amazing, check this third-down strike from Purdy to George Kittle, a quarter of a second before the young passer was crunched by a free rusher. Note the anticipation. 

Unreal courage from the rookie. He was quick to release the football but didn't rush. 

Rookie quarterbacks rush. A lot. Purdy operated exquisitely within the structure of Shanahan's scheme, and even adapted to the Dolphins defensive tendencies later in the game. 

In the third quarter, after Miami had seen a plethora of quick-game, underneath work from Purdy, watch how the defense showed blitz, then backed out to make a wall five yards past the line of scrimmage with four defenders. 

Purdy checked the flat route run out of the backfield by Christian McCaffrey to freeze those defenders, then snapped a throw through that wall to Jennings on a dig across the middle for 15-yard gain on 3rd and 5. 

That's veteran-esque processing and understanding of how to stay a step ahead of the defense. 

Later, on 3rd-and-1 with a six-point lead and under five minutes to go in the fourth, Shanahan didn't put the ball in the hands of McCaffrey, which would've been totally logical. Instead, Purdy play-actioned and quickly got the ball to Kittle in the flat who dove past the first-down marker. 

Purdy had thrown nine passes in the NFL before Week 13. And getting reps in a regular-season game are more valuable than anything else. However, he did start for four full seasons and attempted nearly 1,500 passes at Iowa State. And his arm strength was nothing special in the Big 12. Purdy has long known mastering the intricacies of playing the position -- many of which have nothing to do with physical talent -- is how he can succeed as a quarterback. 

Can the 49ers succeed with Purdy under center? I don't want to get way ahead of myself, but with three of their last five at home and only two contests against clubs in the top 10 in Football Outsiders' defensive DVOA, yes, the 49ers can earn one of the top seeds in the NFC, and given Purdy's mental capabilities, there's a good chance the offensive efficiency dip without Garoppolo is negligible. 

Two weeks ago, I wrote about the 49ers' YAC prowess. Then, right before Thanksgiving, they were tops in the NFL in yards after the catch per reception. After Week 13, they're still at No. 1 in that stat category. 

Once San Francisco's in the playoffs, that's when all of Shanahan's schematic wisdom can't transfer Garoppolo's six games of postseason experience into the mind of Purdy. At that stage, the likes of Trent Williams, Samuel, Kittle, Aiyuk and an incredibly stingy defense will need to elevate their games to guide the rookie in many critical situations. The Eagles and Cowboys bring it defensively. 

Back to that scouting report. I finished with this, which is especially interesting now: 

"Purdy needs to be in a particular, low-risk offense to be maximized at the next level."

He's in the most quarterback-friendly, low-risk offense in football with Shanahan calling the shots. We've seen the 49ers head coach elevate quarterbacks with clear-cut physical deficiencies his entire coaching career. While San Francisco's Super Bowl hopes took a hit with Garoppolo out for the season, at least Shanahan will be tasked to mold a quarterback who has many Garoppoloian traits.