If you're an NFL fan with a pulse, your heart sank a bit on Thursday as you read about Deshaun Watson going down for the remainder of the season with a torn ACL. Every injury is bad, of course, but Watson may very well have been the most pleasant surprise of an often-dour 2017 season. As an exciting young player playing in a city that has been on a roller coaster through tragedy to the joy of Wednesday night's World Series victory, there might be no player in the league that neutral fans would have wanted to see stay healthy more than Clemson's national champion quarterback.

Watson's injury raises all kinds of questions. Let's try to answer a few of them here.

Is there a rash of injuries going around the NFL this season?

It's difficult to say. The attrition rate in the NFL is remarkably and frustratingly high on a year-to-year basis, but it's fair to wonder if this season seems particularly bad. As I mentioned while recording my podcast with Mina Kimes, all you need to do to imagine an injury crisis in the NFL is to watch one or two commercial breaks during an NFL game. You're bound to see ads with Odell Beckham Jr., Aaron Rodgers and J.J. Watt, two of whom are done for the year with the other out indefinitely (Rodgers).

In terms of quarterbacks, let's try to contextualize the problem. As of Week 9, there are six starting signal-callers on the shelf: Watson, Rodgers, Sam Bradford, Andrew Luck, Carson Palmer and Ryan Tannehill. Jay Cutler, filling in for Tannehill, would qualify as the seventh if he's unable to play Sunday.

That's a high number, but not remarkably so. Last season in Week 9, for example, four starting quarterbacks were out injured: Cutler, Robert Griffin, Tony Romo and Alex Smith, the latter of whom would return the following week. At this time 10 years ago, in a 2007 season held up as the peak of football, six would-be starters were out of the lineup. A 1988 Washington Post article complaining about the lack of available quarterbacks noted how 18 passers had gone down with injuries by the end of Week 6, although some of them were not starters.

Only 3 quarterbacks in NFL history have thrown more touchdown passes in a calendar month than Deshaun Watson's 19 in October: Tom Brady, Peyton Manning (twice) and Tony Romo. Photo by Aaron Doster/USA TODAY Sports

Other passers such as Derek Carr and Marcus Mariota have missed shorter periods of time, so let's ask the question a different way. Have we seen more quarterbacks playing meaningful minutes through the end of Week 8 than in a typical year? One way to check for this is by just simply counting how many quarterbacks have thrown a meaningful number of passes -- I'll set the bar at 30 pass attempts -- through the first eight weeks.

We've seen 41 quarterbacks throw 30-plus passes this season, which is right in line with expectations. Since the league expanded to 32 teams and went to its current schedule structure in 2002, an average of 42.7 passers have thrown 30-plus passers through eight weeks, ranging from 35 (2012) to 48 (2002 and 2007). It's impossible to differentiate between injured and benched quarterbacks with this methodology, but given that the figure isn't even at what we would expect given history, it's fair to say that this isn't a particularly egregious year in terms of quantity of injured quarterbacks.

I'd argue we're not dealing with a disproportionate number of quarterback injuries, but the quality of those missing quarterbacks is uncommonly high. I don't think it's necessarily a surprise to see Bradford, Palmer or Tannehill hurt, but consider that we're down arguably the league's most talented quarterback (Rodgers), its most impressive rookie passer (Watson) and a surefire franchise passer in his prime (Luck).

Was Watson off to the best start of any rookie in recent memory?

After coming in off the bench against the Jaguars in Week 1 and struggling through a dreadful Thursday night game -- admittedly one he won for the Texans with an excellent individual effort on a 49-yard TD scramble -- against the Bengals in his first NFL start, Watson was as good as any quarterback in football. After eight weeks, Watson led the league in Total QBR, which includes his exploits as a runner. His 81.9 mark was 7.9 points better than that of Dak Prescott.

Strictly as a passer, Watson was fifth in passer rating and seventh in the league in ANY/A, but even that sells him short. He had drawn eight pass interference calls for a league-leading 173 yards of hidden offense. Watson had thrown eight interceptions, but most of them had come in irrelevant or hopeless situations, as five of them changed Houston's win expectancy by 2.4 percent or less.

Watson threw 204 passes before suffering his knee injury in practice on Thursday. We have to adjust quarterback stats for the era in which they came, which Pro Football Reference does with its index statistics, as 100 represents era-adjusted league-average.

Ninety-eight quarterbacks have thrown 200 passes or more during their debut campaigns since the merger. Of those 98 passers, Watson posted the best touchdown percentage index (152), the fourth-best yards per attempt index (124), and the ninth-best adjusted yards per attempt index (113). The closest rookie quarterback Watson resembles is Mark Rypien, who was actually making his debut in 1988 after two seasons on injured reserve. Rypien started six games during his rookie campaign, and their era-adjusted stats are remarkably similar:

Passer Cmp%+ Y/Att+ TD%+ INT%+ PassRt+ ANY/A+ Deshaun Watson 95 124 152 76 118 113 Mark Rypien 99 128 149 68 113 116

Rypien was already 27 by the time he took over as a full-time starter and really spent only five years as a full-time No. 1 quarterback, but he made it to two Pro Bowls and won Super Bowl MVP for his exploits in leading Washington to the Super Bowl in 1991 during those five years in D.C. Watson has shown similar ability in terms of creating big plays downfield, although he's far more effective as a runner.

Watson's touchdown percentage would have regressed to the mean over a larger sample, but given how both he and the Texans' offense were improving week after week, it seems likely the rest of his game would have kept up. It's impossible to make a perfect comparison because of the smaller sample, but Watson's campaign is certainly in line with that of great recent rookies like Prescott, Matt Ryan, and Russell Wilson as among the best in football.

Does this impact his long-term future?

It's too early to say, but quarterbacks have been able to return from ACL tears without any notable drop off in performance. This is the second time Watson has torn an ACL after doing so in college, but that was an injury to his left knee, while this injury is to his right knee. The promising news is that we haven't heard anything about damage beyond the ACL, which should decrease the complexity of Watson's rehab.

Barring further news on the injury, it seems likely Watson will be ready to return in time for Week 1 next season. While fans might think about Robert Griffin as a worrisome comp for Watson, given that Griffin looked brilliant as a rookie before going down with a knee injury and failing to live up to his previous heights, there are more positive comparables for mobile quarterbacks of the past, too. Randall Cunningham tore his ACL in 1991 and remained effective as both a passer and runner upon returning. Rich Gannon required an ACL repair after going down with a knee injury as a backup in 1988, and the future Raiders standout remained an effective scrambler, though he didn't see serious game time until 1990.

Robert Griffin III had a sensational rookie season in 2012, with 27 total touchdowns and only five interceptions. Adam Bettcher/Getty Images

Should the Texans keep Watson from running as frequently when he returns?

I think Watson would be able to succeed without the threat of the read-option by virtue of his ability as a pure passer, but I also don't see any reason to dramatically change the offense in an attempt to keep Watson healthy. Watson's ACL tears have both come in practice; this most recent injury saw him go down without being touched. If he was getting injured as a scrambler in games, it might be a different story, but the Texans shouldn't need to put any restraints on Watson when he returns.

How much of a drop-off is there from Watson to Tom Savage?

Obviously, there's an enormous difference between Watson and the quarterback he took over for after a dismal Week 1. Savage has yet to show any sign that he's likely to become a competent NFL quarterback. The former Pittsburgh and Rutgers passer failed to show pro-level accuracy as an amateur, and his 105 pro passes have produced a passer rating of 73.9, nearly 30 points worse than Watson's 103.0 mark. Furthermore, it's telling that the Texans drafted Savage in 2014 and yet repeatedly looked outside the organization to add Brock Osweiler and then Watson in lieu of giving Savage the starting job.

The immediate impact in Vegas was significant. The line for Houston's Sunday game against the Colts at the Westgate Las Vegas sportsbook moved by 5.5 points, with the Texans 12.5-point favorites before the Watson injury and seven-point favorites after. Houston was 40-1 to win their first championship before the Watson injury, but they were dropped to 100-1 once news broke.

Should the Texans sign another quarterback?

They already have, at least as an emergency measure. Savage was the only other quarterback on the active roster, as Brandon Weeden was cut after training camp and caught on with the Titans. Bill O'Brien went back to his Penn State days and signed former Raider Matt McGloin, who played under O'Brien in State College during the 2012 season. McGloin posted a 75.3 passer rating over four years as a Raiders backup, throwing 11 picks on what amounts to about a half-season's worth of pass attempts.

The name that will inevitably pop up in connection with this vacancy, of course, is Colin Kaepernick. If we lived in a world in which NFL owners were acting rationally, the Texans would have already signed Kaepernick to fill in. McGloin and Savage haven't been effective in any NFL system and don't have anything resembling the athleticism required to succeed in the offense O'Brien has installed with Watson, which has employed read-option concepts from Watson's playbook at Clemson.

Colin Kaepernick last month filed a grievance under the latest collective bargaining agreement against NFL owners for collusion. Dale Zanine-USA TODAY Sports

Those ideas require the quarterback to be a threat to run and the ability to throw downfield, both of which Kaepernick can do. Much has been made of Kaepernick's supposed inability to throw in the pocket, but his career passer rating in the pocket is 90.3, comfortably better than that of Savage (79.8) or McGloin (78.3). Watson also spent plenty of time bootlegging and scrambling out of the pocket. The rookie threw 45 passes outside of the pocket before going down, second-most in the league behind Russell Wilson.

Two obstacles stand in the way of Kaepernick, who O'Brien called "a good football player" in March. One is Kaepernick's ongoing collusion lawsuit against the league. The other is the presence of owner Bob McNair, who inspired a near-mutiny within the Texans' locker room by referring to the league's players as "inmates" during a meeting with players in New York City.

It's perhaps telling that Texans players essentially appointed left tackle Duane Brown as their representative in light of McNair's comments, only for Houston to subsequently deal Brown to the Seahawks at the trade deadline in lieu of giving their longtime left tackle a contract extension. Could McNair bring himself to sign Kaepernick? Would McNair attempt to sign Kaepernick in an attempt to repair his name? Would Kaepernick even be willing to play for an owner who made such an insensitive remark? We'll see in the weeks to come, but there's no football-related reason to play Savage, McGloin, or any other available quarterback over Kaepernick.

Can the Texans still win the AFC South?

Even with Watson, Houston's chances of claiming a third straight division title weren't great. The Texans were 3-4 and a game back of both the Jaguars and Titans in the AFC South, with the Jaguars holding the head-to-head tiebreaker over Houston after that blowout in Week 1. According to the Football Power Index, the Texans had just a 29.7 percent chance of making the playoffs and a 12.4 percent of winning their division.

Those divisional titles have come with Brian Hoyer (who probably wouldn't have returned to Houston even if the Watson injury had come before he signed with the Patriots) and Osweiler as primary quarterbacks, so it's hardly as if the Texans have needed great quarterback play to succeed. The difference between those teams and this one, of course, is injuries on defense. The Texans are already without Watt and Whitney Mercilus, who are done for the year. Brian Cushing is suspended until Week 14, and replacement Dylan Cole is already out Sunday.

Houston's defense has still impressed for stretches this season -- it ranks eighth in DVOA -- but it has played what amounts to nearly three games without Watt and Mercilus. With the two star edge rushers going down early against the Chiefs, the Houston defense allowed Alex Smith and the Kansas City offense to score 35 points. The Texans then held the lowly Browns to 14 points, but the Seahawks exploded for 34 more points on offense in their classic win over Houston on Sunday.

O'Brien will likely slow down the pace with Savage in the lineup, hoping to win by running the ball and playing sound defense with the guys he has left. Anything is possible, but the Texans have lost two of their best players over the past week with Brown and Watson no longer in the lineup, which will dramatically impact their running game. Unless their defense takes a big leap forward from what we've seen against non-Browns competition, it's hard to find a path in which the Texans compete for the division title.

Who does the Watson injury help?

Obviously, while nobody wants to see a star quarterback get injured, Watson's absence could turn the AFC South into a battle between the Jaguars and Titans. The other team in line to benefit from a Watson injury is the Browns, which acquired Houston's 2018 first-round pick in the trade that netted the Browns Watson in the first place. Cleveland also holds Houston's second-round pick as part of the Osweiler salary dump. Those picks looked likely to come toward the second half of the first round, but with Savage replacing Watson, the Browns could luck their way into another top-10 pick.