College football teams run hundreds of plays throughout the year, but sometimes it takes only one to derail an entire season.

Perhaps no one on LSU’s roster knows that hard truth better than Jalen Mills and Vadal Alexander, two seniors whose past blunders against Alabama ultimately cost the Tigers in the biggest games of two separate seasons.

Alexander still thinks about his mistake. Mills has left his in the past. But both have used their errors as a learning tool — for themselves and their teammates — as LSU prepares for its top-10 duel with the Crimson Tide.

“It’s something to learn from, something to teach my teammates and show them that every single play matters,” Alexander said. “It’s something that motivates me to become a better player.”

No. 2 LSU and No. 4 Alabama, as ranked in the College Football Playoff selection committee’s initial standings, will put Southeastern Conference supremacy on the line when they clash at 7 p.m. Saturday in Tuscaloosa, Alabama.

The Crimson Tide (7-1, 4-1 SEC) have won four straight against LSU, dating to the 2012 BCS Championship Game. The Tigers (7-0, 4-0) are striving to learn from their mistakes to finally swing the series back in their favor and take another step toward a national championship.

Mills and Alexander’s gaffes stand out from the others, coming in the final minutes of tight home games LSU eventually lost on national TV.

The first one featured Mills, then a true freshman defensive back, blitzing hard off the edge with one minute left in a 3-point game. Running back T.J. Yeldon slipped underneath him, wrangled a screen pass and and scampered for a 28-yard score as Alabama escaped its 2012 trip to Tiger Stadium with a narrow victory.

“Just a rookie mistake,” Mills said this week.

Alexander’s mistake came with 73 seconds to play in last year’s meeting, just after the Tigers recovered a fumble on Alabama’s 6-yard line.

The offensive lineman was whistled for unsportsmanlike conduct following the team’s first offensive play, and LSU settled for a field goal before Alabama kicked one of its own to force overtime, where the Tide again snatched the win.

Not every error is as glaring as those Mills and Alexander committed. Several smaller, less visible blunders that seem less costly at the time permeate every game.

But those mistakes accumulate, and players know the room for error is almost nonexistent when LSU and Alabama get together.

“It sticks with you because you work so hard and then it’s taken away from you,” junior defensive end Lewis Neal said of the close losses. “You can’t let that take control of your emotions. We’ve just got to execute, do what we do and not make the mistakes we made. We’ve gotta learn from those mistakes we made the last time.”

Players took that to heart the last two weeks, using the open date to fix their own flaws before preparation for the Tide began. Alexander was one of a handful who looked no further than his own performances against Alabama when self-evaluating.

“I watched all three of those games over and over again these past couple of days to just learn from the mistakes and try to improve in this matchup,” Alexander said last week.

Past mistakes may linger in some players’ minds, but Alexander is fine with that. The senior maintained players learn more from wins than losses, and the Tigers have had their share of losses to the Tide over the past few years.

“I haven’t seen a great player not make a mistake before in their life,” Alexander said. “Great players will always make mistakes. It’s what you do to prepare to not let it happen again.”