When Paul Mainieri slips into bed at night, he’s often thinking about third base.

When the LSU baseball coach wakes up, he’s often thinking about third base.

“I lose sleep at night,” he said.

Mainieri lost what he calls the best third baseman he’s ever coached.

Christian Ibarra’s baffling barehanded plays, his rifling throws to first, his silly foul line dives are gone. He’s exhausted his eligibility and is now an undergraduate assistant coach with the team.

He’s helping school three players — Danny Zardon, Conner Hale and Greg Deichmann — who are competing to fill the void he left at a spot known as “the hot corner.”

“I don’t think he’s replaceable,” Hale said of Ibarra.

LSU begins practice for the 2015 season on Friday with two areas of concern. The inexperience at pitcher — two of three weekend starters could be true freshmen and another could close games — and, of course, replacing Ibarra at third.

They are both keeping Mainieri up at night. Everything else? It looks dandy. Even national outlets can see that. LSU is ranked in the top 10 in all three preseason polls released so far.

Tyler Moore and Sean McMullen are the only significant losses in the nine-man lineup, the bullpen is seasoned and LSU’s defense, specifically in the outfield and at shortstop, may be one of the best in the nation.

And then there’s third base. Zardon, Hale and Deichmann are competing for the starting role. Zardon, a sophomore from Florida, is the leader, for now, and is expected to get the first shot at the position.

No matter what happens, Hale will be in the lineup every day, Mainieri said. Hale, who rooms with Zardon, split time between first and second base last season.

LSU would have more flexibility with its lineup if Zardon or Deichmann do well enough to win the starting job at third. Hale could move back to the right side of the infield, giving Mainieri opportunities to use a variety of lineups.

For now, competition rages.

On a sunny afternoon at Alex Box Stadium earlier this week, the three players fielded balls from Mainieri. Zardon emerged from the 40-minute session having committed the fewest mistakes and having made the most difficult of plays.

There was the short hopper that Zardon corralled down the third-base line and slung, perfectly, to first base; the surprising line drive he snared; and all of the routine plays he made look … routine.

He showed off a powerful arm, quick reaction time and veteran poise.

It shouldn’t be too surprising. After all, Zardon has played third base his entire baseball career, aside from one high school season as an outfielder.

He was good enough last year as a true freshman for Mainieri to start him in 13 games, including six at first base and five at third. He hit a grand slam against Yale, fielded at a .984 clip and drove in 10 runs in 56 at-bats.

Mainieri has delivered a message to Zardon: Offense doesn’t matter.

“Regardless of how I hit, it’s not going to be enough,” Zardon said. “You can’t have one bad day defensively.”

“We can’t sacrifice defense at third base in the name of offense,” the coach said.

Third base doesn’t get the kind of spotlight that shortstop, second base or, even, first base does. It doesn’t get the kind of action.

For instance, Ibarra had 148 total chances last season. Six everyday position players had more. Four of the six had more than 200 chances and two had more than 325.

The opportunities at third are fewer, but more difficult and loom larger, Mainieri said.

“In today’s day and age of college baseball — because there’s not the free-swinging home-run hitting games of years gone by — the bunt has become a much more usable play and there’s been an awful lot of chopped balls in the infield,” he said. “Third-base defense is one of those things you take for granted until you don’t have it.

“It’s an unbelievably difficult position to play.”

Ibarra had fielding percentages of .932 last year and .934 the season before. He had 22 errors out of a combined 329 chances the last two seasons. Tyler Hanover in 2011 and 2012 had fielded .939 and .929.

That’s a good four-year run after the struggles at third base in 2010, a season that “haunts” Mainieri, the coach said.

Four players started at least eight games at third base that season. They averaged a fielding percentage of .901.

“I thought our lack of defense at third cost us that year,” Mainieri said. “I thought our team was good enough to go to Omaha except for the void at third base.”

There’s a void again that must be filled. While Zardon might be viewed as the leader, Hale’s the fallback guy and Deichmann is the darkhorse.

Deichmann, a highly recruited shortstop out of Brother Martin, had never played third base until making the switch during summer ball last year. He’s noticed an obvious change from shortstop to third: “You don’t have much time to get to a ball, set up and throw,” he said.

He’s playing some second, too. Mainieri doesn’t see him as a shortstop.

For now, Deichmann’s concentration is winning the starting job at an all-important position.

“It’s a tough competition, but no one is pulling against each other,” Deichmann said. “Everyone wants each other to succeed. May the best third baseman win.”

Follow Ross Dellenger on Twitter @DellengerAdv.