Three and four years ago, they were bewildered freshmen. B-back David Sims recalled that his first preseason camp at Georgia Tech included “a lot of yelling, a lot of confusion and a lot going on.” Offensive lineman Will Jackson was introduced to college football by eventual first-round NFL draft pick Derrick Morgan, who flattened him in a drill.

“I just remember, at the time, coming into camp I didn’t think I was going to redshirt, and I thought I was going to play,” Jackson said. “At that moment, I was like, OK, I need a year to get stronger.”

Tech’s 18 seniors have come almost to the end. The fifth-year seniors who arrived in 2009 and watched their teammates win the ACC title and the fourth-year seniors who arrived a year later make up the largest senior class since coach Paul Johnson’s first season, in 2008. With such a significant presence — 12 of the 18 are expected to start — the Yellow Jackets are counting on their leadership and play.

“Hopefully, it’ll allow the team to lean on us,” Sims said Thursday, following Tech’s first day of preseason camp. With so many seniors and senior starters, “I think that’s something that we really need to take advantage of.”

Tech enters the season with 330 combined career starts on the roster, by far the most of any Johnson team at Tech, almost 100 more than last season’s team. That includes Jackson, a three-year starter, and seven two-year starters.

The heavy senior class “means you’ve got some guys that have played a lot of football, normally, which is a good thing,” Johnson said.

It doesn’t mean much to observers. The Jackets were picked to finish fourth in the ACC Coastal Division. Tech did not receive a vote in the USA Today coaches poll, released Thursday, the first time that has happened in at least 15 years.

Said Sims, “We’re used to not getting respect.”

Voters, perhaps, see a team that finished 7-7 last season, 8-5 the season before and 6-7 the one before that, and not necessarily what the Jackets see in themselves — a team that finished last season strong, came within a touchdown of winning the ACC championship, beat USC in the Sun Bowl and is revitalized by new defensive coordinator Ted Roof.

“You want to improve your game and you want to come back and do better than before,” said safety Isaiah Johnson, a senior and two-year starter coming back from an ACL tear. “Just like track, you set your (personal record) and you try to break that.”

Sims has a lofty vision for his final season in white and gold — one that would stun the voters and, presumably, all of college football.

“An undefeated season and a bowl win,” he said. “That’s all I want.”

Sims, who redshirted in 2009 in Tech’s ACC title season, sees a chance to bookend his career with championships and leave things as he and his freshman classmates found them.

“We won seven and eight (games) those (past) two seasons,” he said. “There were at least two or three games that we probably should have won, so that’d be — what? — 10 or 11 wins a year. That’s the legacy we’re trying to leave.”

Practice report: Tech opened its camp down four offensive linemen, one permanently. Lineman Catlin Alford has left the team, coach Paul Johnson said, and may leave school.

Alford, a junior, had played a backup role in his first two seasons with the Jackets. Johnson said Alford told him that he was tired of playing.

“It happens sometimes,” Johnson said. “I tried to encourage him to come back and finish school, because he’s so close (to graduation), and I think he’s going to transfer to a smaller school somewhere.”

Offensive tackle Morgan Bailey will be out with an unspecified injury for six weeks, Johnson said. Bailey, who has had a history with injuries, started seven games last season and is being counted on as a starter. His absence opens room for sophomore Bryan Chamberlain.

Center Jay Finch, a two-year starter, practiced in a gold jersey, meaning he was kept out of contact drills. Finch underwent shoulder surgery that kept him out of spring practice. Johnson said Finch should return to practice before camp ends. The absence of Finch and Alford, along with Freddie Burden, who also likely will miss the season with a knee injury, means Tech’s top three centers are out. Offensive tackle Ray Beno will sub in Finch’s place until his return.

A-back Robert Godhigh also is temporarily out, healing from a broken hand. He was in a cast Thursday. He should be back “in a week or so,” Johnson said. Safety Isaiah Johnson, returning from an ACL tear, also was in a gold jersey.

“We’re going to kind of ease him back in,” Johnson said.