With the biggest night of the preseason (in terms of number of games played) now behind us, it's time to review what we've learned from four weeks of exhibition matchups. There were certainly some highs and lows, with major takeaways to keep in mind as we count down to Week 1 kickoff.

1. The Vikings' season is likely done before it started.

Teddy Bridgewater was having a great preseason, ranking among the best-graded QBs in the league over three games. He had only taken 28 dropbacks, but had completed 78.3 percent of his passes, thrown for a couple of scores, and earned a 141.5 passer rating, showing the kind of deeper passing the Vikings have been trying to coax out of him. Then a freak non-contact injury in practice saw him tear his ACL and dislocate his knee, putting him out for the year and throwing the entire Vikings season into jeopardy. They are now riding Shaun Hill into the season and looking for an answer at QB.

2. Olivier Vernon looks like the player that ended 2015, not the guy that started it.

The Giants' signing of DE Olivier Vernon to a big-money contract based on a monster stretch of eight games to end the 2015 season was always going to be a risk, but over 81 preseason snaps, at least, Vernon looks like the same guy from that devastating run of play. He has notched a sack, two hits, and six hurries from 46 pass-rushing snaps giving, him the second-best pass-rushing productivity mark among 4-3 defensive ends this preseason. The Giants need Vernon to produce, and he looks motivated to do so.

3. Vernon Hargreaves could make a huge impact as a rookie.

Always a ballhawk at Florida, Buccaneers CB Vernon Hargreaves was shutdown during the preseason—almost entirely, in fact. He was thrown at eight times, allowing one catch for 2 yards. He caught more of the passes sent his way (two) for interceptions than he allowed receivers to catch. Hargreaves also broke up another pass, and for the entirety of preseason, QBs targeting him had a passer rating of 0.0, or almost 40.0 points lower than just throwing the ball into the dirt every play.

4. Backup offensive linemen are generally terrible.

The league has an offensive lineman problem in general, but when you get to the third-team line in the preseason, you are suddenly grateful for even the worst starters. In the 2015 regular season, there wasn’t a single tackle, guard, or center with a pass-blocking efficiency lower than 90.0, putting the entire league in a 10-point spread between 90.0 and 100.0. In this preseason, that spread extends another seven points, with the lowest-ranked tackle posting a mark of 83.8, and surrendering 19 total pressures on 95 passing snaps. No matter how bad your starter is, just be thankful he’s not one of these third-string guys.

5. Derrick Henry may have been undervalued in the draft process.

Titans RB Derrick Henry has been impressing in each preseason game. He ended the preseason with 34 carries for 216 yards (6.4 per attempt), with 137 of them coming after contact (4.0 per attempt), breaking 12 tackles and scoring three times. It looks like his freakish blend of size and quickness is still just as effective against NFL-level athletes, and he may have been too harshly viewed in the draft process because of fear that his abilities would not translate once the level of opposing athlete stepped up.

6. OTs rarely grade well from day one—Ronnie Stanley looks like he can.

In 81 snaps of action with Baltimore's first team this preseason, LT Ronnie Stanley has allowed just two hurries, and has yet to be to blamed for the QB hitting the ground. He hasn’t picked up a penalty of any kind, and even has a strong run-blocking grade, looking every bit the high first-round draft pick he was. Offensive tackles usually struggle early, but so far, Stanley has looked like a seasoned vet.

7. QB Christian Hackenberg does not look ready to play in the NFL.

This is hardly a surprise given his college tape, but Jets second-round pick Christian Hackenberg is not going to be anywhere near the field in 2016, barring some major unforeseen developments. He was barely taking reps during camp, and only played in the final two preseason games, totaling 73 snaps of action. He led a nice touchdown drive in his first game, showing the flash of talent that baits the hook before the disastrous play that inevitably follows. Follow it did, with two interceptions to come and a passer rating under pressure for the preseason of 1.7.

8. The Tajae Sharpe training-camp hype was legit.

The fifth-round rookie was making waves in Titans camp from day one, and hit the preseason as a starter in this offense. He ends it not just proving that hype correct, but probably emerging as the team’s No. 1 receiver. Sharpe caught nine of the 12 passes thrown his way for 163 yards, and though he failed to find the end zone, he did have several big plays and clutch catches. For a guy who doesn’t seem to have anything spectacular in his arsenal, Sharpe does everything well.

9. Dallas found a backup QB at the right time.

Tony Romo is always one play away from a significant injury that puts him out of action—and the Cowboys' season in peril. Usually that hit comes during the regular season, but this time it came before opening day. Luckily, the Cowboys look to have struck gold in Dak Prescott, a rookie fourth-round QB who has had an excellent preseason. After the first game, he had won the backup job, and by the end of the second, he had people excited about his potential. He ends the preseason having completed 78.0 percent of his passes with a passer rating under pressure of 127.3—which is just as well, because he is the Cowboys' Week 1 starter.

10. The preseason is a week too long.

The NFL preseason is a necessary evil, but it only makes sense to get players ready for the regular season if they’re actually playing in the games. The final preseason game has long been one in which the majority of starters are rested, but now teams are treating the second preseason game as more of the same, and even the third preseason game—the one typically the closest to live regular-season action—is seeing starters take just a quarter of football before retiring to the bench. At this point, we could easily dial it back and accomplish the same things in just three games.