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LSU assistant coach Nolan Cain speaks to LSU left fielder Antoine Duplantis (20) and LSU shortstop Kramer Robertson (3) as they switch to defense in a game against Ole Miss, Thursday, April 13, 2017, at LSU's Alex Box Stadium, in Baton Rouge, La.

Before this season started, LSU and South Carolina occupied some of the loftiest positions in the country.

Both were consensus top-five teams in the various preseason college baseball polls. Both expected to make deep runs in the NCAA tournament, with experienced and talented rosters.

But 2017 hasn’t gone to plan.

The Tigers are on the upswing, but they've had some low moments. A team that had the College World Series on its mind in February didn’t look like an NCAA regional host in Southeastern Conference series losses to Florida, Texas A&M and Kentucky.

The situation is a little more dire in South Carolina. The Gamecocks come into Alex Box Stadium this weekend desperate for some good news.

They have lost five consecutive SEC series, dropping to 10-11 in conference play. They are four games back of Eastern Division-leading Kentucky with three weeks left in the regular season.

South Carolina, ranked No. 4 or 5 in each major preseason poll, is just eight games above .500 as it begins its May schedule.

A couple factors have led to LSU and South Carolina's slide. Among them:

1. Injuries to important players

LSU had a couple significant blows before the calendar even flipped to March.

About a week before the season opener, the Tigers lost designated hitter and projected cleanup hitter Bryce Jordan for the year. On Feb. 27, the club announced that setup man Doug Norman would miss the rest of the year with a torn ulnar collateral ligament.

The Tigers have only lately found the best replacements for Jordan and Norman in newcomers Nick Coomes and Zack Hess.

LSU also had to go three weeks without closer Hunter Newman, who was dealing with a back injury. The Tigers' best slugger, Greg Deichmann, is still wearing a mask on his helmet; one week before the opener, he was struck in the face by a pitch.

Even though it happened recently, the Gamecocks must finish the season without junior right-hander Clarke Schmidt, who had season-ending surgery last week after accruing a miniscule 1.34 ERA in nine starts.

It’s tough to ask a struggling team to right the ship without its ace pitcher.

2. Down years from key contributors

LSU figured to have a fearsome trio at the top or middle of the order in Kramer Robertson, Cole Freeman and Antoine Duplantis. But that trio has had a rough go of it in SEC play, batting just .264 as a group.

Last season, Robertson, Freeman and Duplantis combined to hit .323 in SEC play. That certainly has not been LSU’s only issue, but the Tigers are scoring 5.7 runs per game in SEC play compared to 6.2 last year.

Take away the 22- and 15-run outbursts against Georgia and Ole Miss (they account for 31 percent of the runs LSU has scored against the SEC this year), and that average drops to 4.3 runs per game.

But imagine what LSU’s offense would’ve looked like if Greg Deichmann had a down season. That’s what happened to South Carolina and outfielder Alex Destino.

Destino was one of the league’s top returning hitters, having batted .321 with 10 homers and 59 RBIs as a sophomore. But he has not been able to replicate his production.

In 39 games this season, Destino has hit .255 with five homers and 25 RBIs. Against SEC pitching, he is hitting .214 with seven RBIs. He was recently benched for a portion of the Gamecocks' series loss to Kentucky.

3. Poor performance late in games

This has actually been the difference between South Carolina and LSU.

The Tigers may have been inconsistent through 45 games, but they enter this weekend as a consensus top-15 team because they’ve won many of those 45 games.

LSU has 30 wins. In 26 of those wins, the Tigers either tied or had the lead after seven innings, and they lost just two of those games.

South Carolina, meanwhile, has 17 losses. Seven of those have come when it was tied or leading after seven innings.

The Gamecocks have had the opportunities to win. Unlike LSU, they haven’t cashed in on them.

This weekend is important for both teams.

LSU can build on some of its positive momentum from last weekend’s sweep of Alabama as it tries to erase the one-game deficit it faces in the Western Division standings. The Tigers seem to have taken a step back for every step forward this season. They cannot afford to do that again with so little time remaining.

The Gamecocks, meanwhile, have a favorable schedule after they play LSU, with series against Missouri and Georgia at home. A big series win at Lex Box could propel them to a strong finish.

LSU could still win the league with a series loss, and still come close to meeting its lofty expectations.

At this stage, you can’t say the same for South Carolina.

Follow Luke Johnson on Twitter, @ByLukeJohnson.