You don't need to wade into Pro Football Focus' sea of statistics to notice the NFL has a widening gap between the quality and quantity of its great pass rushers and the poor fellas trying to block them.

Monday's game between the Giants and Lions was a sturdy exclamation point to that early NFL trend.

The defenses that night had eight sacks while allowing only 327 net yards passing combined. The Lions gave up three sacks, posted 119 net passing yards and won by 14.

The left tackles struggled, to put it kindly. The Giants' Ereck Flowers gave up three sacks. Detroit's Greg Robinson was flagged three times, gave up a sack and was the primary reason we got to see the leaner Matthew Stafford showcase his new run-for-your-life gear.

To see Flowers and Robinson punished in prime time illustrates just how desperate the league is at left tackle in particular and offensive line in general. After all, Flowers was the ninth overall pick in 2015, while Robinson was the second overall pick in 2014.

Robinson is only 24 years old, yet he already has been cast aside for a sixth-round draft pick by the Rams team that drafted him. And he's starting in Detroit only because the Lions were desperate when Taylor Decker underwent shoulder surgery.

Robinson, of course, isn't the only example of even highly drafted linemen fizzling quickly in the NFL.

Luke Joeckel was the second overall pick in 2013. He was going to be Jacksonville's left tackle for 10 years. Four years later, he's the left guard on a line that's probably going to torpedo Seattle's Super Bowl aspirations.

In Week 1, it was Joeckel who helped Packers defensive tackle Mike Daniels impersonate Mean Joe Greene. The play of the game in that Packers win was Daniels beating Joeckel and strip-sacking Russell Wilson inside his 10-yard line.

So why the widening gap?

The popular notions are the over-simplified protection schemes in college and an NFL Collective Bargaining Agreement that has reduced practice time and the amount of time spent in full pads.

"I'm not trying to blame college, but it's all the spread stuff you see," Vikings coach Mike Zimmer said. "It's slide one way, slide the other."

And that's pretty much it as far as college protections go.

"My rookie year in San Diego, [defensive end] Dwight Freeney was there and he told me he thinks it takes an offensive lineman four or five years to be great in this league," said Vikings backup lineman Jeremiah Sirles. "He said college linemen coming in don't know the different protections, the different sets, how to use their hands. Playing O-line in the NFL has to be learned in the NFL."

Meanwhile, the college game sharpens great athletes into great pass rushers, making more of them ready-made weapons at the next level.

"There are some tremendous pass rushers coming out of college football," Vikings offensive coordinator Pat Shurmur said. "My boy [Vanderbilt quarterback Kyle Shurmur] plays in the SEC and I watch it every week. I watch what's going after him every week."

Meanwhile, the large men trying to block these college rushers become pass blocking toddlers at the next level. Throw in the fact that offensive linemen need to learn how to play in unison with four other linemen and, well, it becomes an issue.

"I do think, because of the rules of training here in the offseason that we have now, there really is no contact, per se," Shurmur said. "That's how an offensive lineman needs to work. He needs to be engaged with somebody."

In a cyclical league, one way to rebalance the scales is to go old-school and run the ball with more brute force.

"These great pass rushers are mostly 250-pound specialists," said former All-Pro NFL linebacker Chris Spielman, who will work Sunday's Buccaneers-Vikings game as Fox's analyst. "When it's second-and-long, they have money time in their heads. They're thinking sacks. If it's second-and-short, they have to think about more than chasing the quarterback."

Mark Craig is an NFL and Vikings Insider. Twitter: @markcraigNFL