One of the things that makes Major League Baseball the best sport is its ability to suddenly and completely shatter your heart. And then stomp on the pieces.

With a long, grinding season and a high level of competition, many teams that look great near the halfway point of the season end up collapsing down the stretch. It doesn’t happen often, but when it does, fans, players and managers remember it forever.

Regular Season Collapses

Here’s a list of six such collapses that have taken place just this century (we don’t have the heart to reopen those really, really old wounds). Take it as a history lesson and mid-July cautionary tale for fans of the teams currently in first place.

2014 Oakland Athletics

The A’s held an eight-game lead over the Los Angeles Angels in the American League West on Aug. 5. They then acquired veteran pitcher Jon Lester to prepare for their playoff run. Then the train ran off the track. The A’s lost 23 of 35, the Angels began winning (including a 10-game win streak), and by season’s end the A’s finished 10 games behind the Angels.  They made the playoffs as a wildcard, but lost the wildcard game to the Kansas City Royals after blowing a 7-3 lead.

2003 Seattle Mariners

The Mariners had a Major League-best 48-22 record in mid-June and led the A’s by 7 ½ games in the AL West. They then gave fans a long, slow collapse, which arguably is worse than a sudden one. For the rest of the season, they finished two games under .500. They missed the playoffs altogether, losing the division to the A’s and a wildcard spot to the Boston Red Sox.

2011 Atlanta Braves

In the 2011 season, everything went right for the Braves right up until September. The Philadelphia Phillies that season had command of the National League East, but the Braves looked to be a lock for the wildcard. As September started, they had an 8 ½ game lead in the wildcard race. By the end of the season, they had gone 9-18 in September. In the last game of the season, they had to beat the Phillies to make the playoffs. Instead, they lost in 13 innings.

 2009 Detroit Tigers

There are many ways to look at how bad the Tigers collapsed in 2009. For example, they were either alone in first or tied for first in the AL Central from May 16 through Oct. 6. They had a seven game lead in the division with just 26 games left to play. They still had a two-game lead after 155 games.

But the worst way? They had a three-game lead over the Minnesota Twins with just four games left to play. Then, they lost a game against the Twins. Then, they lost two out of three games against the Chicago White Sox to end the season, while the Twins swept the Kansas City Royals to tie the Tigers for first. In the one-game playoff to decide the division, the Twins won in the 12th inning, making the Tigers the first team in the long history of Major League Baseball to blow a three game lead with four games left.

2007 New York Mets

Still a painful topic in New York City, unless it’s discussed by Yankees fans. The Mets held a seven-game lead with just 17 games left. They had a more than 99 percent chance of making the playoffs. So much for math. The Mets won just five more games, losing the division to the Phillies and wildcard spots to the San Diego Padres and Colorado Rockies.

Now, remembering these regular season collapses doesn’t mean that fans of the current division leaders – the Boston Red Sox, Cleveland Indians, Houston Astros, Washington Nationals, Milwaukee Brewers, and Los Angeles Dodgers – should feel nervous. Those teams are in a far better position than the other 24 MLB teams.

But the potential for heartbreak is there. In baseball more than any other sport, “It ain’t over ‘til it’s over.”