Deshaun Watson's first real college football action came in Tallahassee against defending national champion Florida State in 2014. He completed 19 of 28 passes in a near-upset. A couple of months later, in his first rivalry game with South Carolina, he went 14-of-19 passing for 269 yards ... with a torn ACL.

In Watson's first full season as a starter, he threw for 4,100 yards, finished third in the Heisman voting, led Clemson to a 14-0 start and national title game appearance, and lit up Alabama's defense for 40 points in the final.

Four games into Watson's junior season, he's an afterthought. Clemson is 4-0 and controls its destiny in the quest for a second straight Playoff bid, but the Tigers sunk three spots in the polls to No. 5 during an underwhelming September. And Lamar Jackson and No. 3 Louisville have stolen the headlines leading into Saturday night's huge battle in Death Valley (8 p.m. ET, ABC).

Jackson has been incredible. The sophomore is on pace for 4,000 passing yards, 1,500 rushing yards, and 75 combined touchdowns in 2016, and even if that pace falters ... holy hell, what a pace.

Now Jackson has to out-duel the preseason Heisman favorite and presumed No. 1 draft pick.

It's safe to say Louisville is going to score, even against a Clemson defense that currently ranks first in Def. S&P+. But the host Tigers will have a chance to answer.

Two weeks ago, following a lackluster Clemson win over Troy, I attempted to dive into the cause of the Tigers' struggles.

Against Auburn, Clemson's biggest issues were a lack of run efficiency, iffy drive finishing, and the inability to make enough big plays to counter inefficiency. Wayne Gallman gained 5 yards or more on only 11 of 30 carries and gained more than 11 yards just once. [...] Against Troy, it was a similar story. Gallman was even less effective, rushing for 5-plus yards three times in nine carries -- that he got only nine carries seemed like compensation for the fact that Clemson's rotation wasn't very large in the opener -- and only Watson himself could bring any efficiency to the ground game. This rendered Clemson one-dimensional.

Through the first seven or so quarters of the season (four against Auburn, three against Troy), Clemson averaged only 4.7 yards per play; the Tigers needed countless defensive stops to survive Auburn, then a few late scores to get past Troy. But they got those scores, and including the last two games (a 59-0 romp over SC State and a 26-7 win at Georgia Tech), they have now averaged 6.2 yards per play over their last nine quarters.

Perhaps that's a sign of growth. But the Tech game didn't provide utmost assurance. Tiger efficiency was where it needed to be — 62 percent success rate in the first quarter, 57 in the second — but Clemson still couldn't generate many big gains and faltered constantly before reaching the end zone.

Through four games, Clemson has only four gains of 30-plus yards.

Only four teams have fewer: Bowling Green, Buffalo, Kent State, and Texas State. Two have played only three games. And of those four big gainers, none came via rush.

Bruising back Gallman has basically reproduced last year's efficiency numbers — 38.3 percent of his carries have gained at least five yards, compared to 40.3 percent last year — but he barely, if ever, gains more. His per-carry average has sunk from 5.4 yards to 4.1 because of it.

You can survive without big plays. Navy has for years. (Granted, Navy doesn't have Watson, Gallman, Mike Williams, Ray-Ray McCloud, Artavis Scott, Deon Cain, etc.) Scoring without explosiveness requires consistent execution. Any penalty or loss virtually ends a drive.

A lack of big plays puts a lot of pressure on you to execute in the red zone; you aren’t scoring from 40 yards out, so you have to continue moving as the defense gets more packed in. Clemson has struggled drastically. The Tigers average just 4.5 points per scoring opportunity (first downs inside the opponent’s 40), 87th in the country.

There have been plenty of culprits. The line has clearly been substandard — losing tackle Joe Gore and all-conference guard Eric Mac Lain has affected that. Meanwhile, though Watson and Williams have a solid rapport following Williams’ return from 2015 injury (Williams is averaging 9.2 yards per target with a 52 percent success rate), miscommunication has been a problem.

The Tigers still have Watson, though. And it appears they’ve been saving him for a moment like this.

Watson’s carries have become less frequent this year, and there are likely a couple of reasons.

First, it’s pretty common to want to protect your quarterback more as the NFL Draft approaches; second, it appears to be something the Tigers have tactically held in reserve.

Thus far, Watson has been Clemson’s short-yardage guy. In 31 carries against Auburn, Troy, and Georgia Tech, 15 came in either goal-to-go situations or second-, third-, or fourth-and-short. He rushed only three times per game on first down. It has worked — Clemson is undefeated, after all.

But the Tigers might need more from Watson’s legs on Saturday night. And if his career has been any indication, they’ll get it.

To the credit of head coach Dabo Swinney's staff, they seem to understand the season is a marathon and not a sprint.

Watson finished with 13.8 carries per game last year, but that increased as the season progressed. He averaged 9.1 carries per game over the first seven, 13.5 over the next four, and 22.3 over the final four. Through four games this year, he’s at 8.8.

There’s another way of looking at last season’s numbers. He averaged 20 carries per game against ranked opponents and 10.7 against unranked.

Louisville is ranked third. Expect a heavy dose of Deshaun.

Will it work, though?

Watson has been somewhat effective in those short-yardage situations. On third-and-3 or fewer against FBS opponents, he's moved the chains eight of nine times. But he was also stuffed on a fourth-and-1, and in three goal-to-go carries, he twice lost yardage.

As ESPN’s David Hale pointed out, Watson has not only run less frequently, he’s also been less effective.

Watson ran by design once every 10 offensive plays last year. This year, he’s doing so every 14 plays, or approximately 40 percent less. And while Watson is running less often, he’s also running less effectively. Last year, he averaged 5.94 yards per run through four games. This year, just 4.03 — a 32 percent drop. That can almost entirely be explained by the offensive line. Watson’s yards-per-rush (not counting sacks) average before contact has been cut nearly in half, from 4.09 per carry to 2.24.

Part of that has to do with down-and-distance; you’re more likely to draw early contact on third-and-2 than on first-and-10. But in the three games from which I’ve been drawing a sample, he also gained 3 or fewer yards on 6-of-9 first-and-10 carries.

Clemson’s line simply hasn’t met the standard. That must change immediately.

While Louisville hasn't been incredible against the run -- 33rd in rushing success rate allowed, 84th in IsoPPP (which measures the magnitude of the successful plays) -- the Cardinals are aggressive and invasive. They are just 100th in power success rate allowed, but they make run stops at or behind the line of scrimmage 26.1 percent of the time (19th). Linemen Chris Williams, DeAngelo Brown, and Kyle Shortridge have eight non-sack tackles for loss.

If Louisville can leverage Clemson into second- or third-and-long, the Cardinals will force the Tigers to make the big plays they haven't.

And they will have to do so in the face of a serious pass rush. Louisville is eighth in passing downs sack rate, eighth in completion rate allowed, and 19th in overall havoc rate. They know what to do when you are behind schedule.

"I always tell them, 'You eat an elephant one bite at a time.' Some bites have a little more juice to them than others. This is going to be a fun one." — Dabo Swinney

A month ago, we were looking at Clemson’s slate as a one-game schedule — if the Tigers could beat Florida State, they were all but in the Playoff.

But before they can make that trip south, they now have to survive as a 2-point home underdog.

While the marquee battle will take place when Jackson tries to move the ball against Clemson’s immovable defense, Watson and company will tell us whether the Tigers can keep eating the elephant.