In a year when the Houston Texans have already lost J.J. Watt and Whitney Mercilus to injury, the team suffered its most significant blow this week. According to multiple reports, quarterback Deshaun Watson tore the ACL in his right knee during Thursday's practice, ending an extremely promising rookie season after just seven games.

The Texans' transformation from a pedestrian offensive attack a year ago (17.4 points per game, No. 28 in the NFL) to a premier scoring unit in 2017 (30.7, No. 1) was all Watson. He replaced Tom Savage, the team's original starter, midway through the team's Week 1 tilt with the Jacksonville Jaguars. The following week, Houston notched its first win. A week after that, they nearly upset the defending champion New England Patriots. With Watson at the controls, the Texans had scored at least 33 points in their past five outings and clawed back into playoff contention.

Watson's torn ACL immediately halts that progress. The Texans have yet to make his injury official, listing him only as a limited participant in Thursday's practice. His teammates have effectively confirmed the news on social media, though, with Watt and others offering their support.

While ACL tears no longer carry the same ominous overtone they once did, knee reconstruction remains a tricky operation from which quarterbacks recover differently. Tom Brady blew out his knee during the first week of the 2008 season, returning a year later no worse for wear. On the other end of the spectrum, Robert Griffin III never came close to replicating his Offensive Rookie of the Year campaign after tearing his ACL in his first playoff game. Most players who suffer severe knee injuries fall in between those extremes, with Carson Palmer (2005) and Sam Bradford (2013) requiring multiple years before fully recovering.

On the surface, the more a quarterback relies on mobility, the more they struggled to rebound from knee reconstruction. For Watson, who just a week ago became the first player in NFL history to rush for 50 or more yards while passing for at least 400 yards and four touchdowns in the same game, the road to recovery could be long.

The Texans do have some reason for optimism, however. Watson has gone through this process before, tearing the ACL in his other knee during his freshman year at Clemson. He recovered quickly and started every game the following season, delivering his best statistical campaign in the process. Watson passed for over 4,100 yards, 35 touchdowns and 13 interceptions. Perhaps most significantly, he rushed 207 times for 1,105 yards and 12 touchdowns. That strong return suggests that Watson can bounce back again.

Regardless, the Texans must now begin the second half of the season without their most valuable and dynamic offensive player. Savage returns from the bench to QB1, presumably for the remainder of the season. He has shown little in his three career starts, completing exactly 60 percent of his throws while passing for just 263. Most revealingly, Savage has yet to throw a touchdown in the NFL.

With no other healthy quarterback on the roster, the Texans quickly signed free-agent passer Matt McGloin, who played for Houston head coach Bill O'Brien at Penn State but has lingered on the open market since the Philadelphia Eagles axed him during final cuts in September. Like Savage, his has a spotty track record in the NFL, completing just over 58 percent of his passes while throwing as many touchdowns as interceptions (11 each).

With no field-tilter under center for the duration of the year, the Texans will look decidedly different on offense. Watson negated the impact of a bad offensive line with his mobility and kept opposing defenses from stacking the box with his arm. His play put wideout DeAndre Hopkins on pace for 103 catches, 1,385 yards, and 16 touchdowns while running back Lamar Miller appeared set to finish near 1,000 rushing yards for just the third time in his career. On a macro level, Houston has virtually no chance of finishing atop the NFL in scoring.

But while the Texans will regress on offense without Watson, O'Brien can adjust his approach to fit his remaining personnel. Miller remains an effective ball carrier and rookie D'Onta Foreman has flashed promise in his limited snaps. Both should see more work in the wake of Watson's injury. As for the passing game, DeAndre Hopkins could spend more time in the slot and running quicker-developing routes to account for his new quarterback's limitations. Tight end Ryan Griffin could also see an uptick in usage. Houston will still use Will Fuller to stretch opposing secondaries, but his red-hot October -- nine catches for 244 yards (27.1 per reception) and five touchdowns -- seems unlikely to continue into the final months of the season.

Still, no schematic changes can fully account for the loss of Watson, an Offensive Rookie of the Year frontrunner and MVP candidate. The Texans, currently 3-4 and next to last in the AFC South standings, already had little margin for error. Unless O'Brien can pull off one of the all-time great coaching performances, their path to the playoffs appears irreversibly blocked.