Being on top of the standings at the beginning of the year is great, but what really matters is having one of the best records in baseball after the last day of the season.
Throughout baseball history, there have been a number of teams that looked like World Series contenders that have struggled late in the year. In some cases, these teams have lost playoff spots as a result.
The New York Yankees had a big lead during the 2012 season and have seen it dwindle down due to their recent struggles. They could end up having one of the worst collapses in baseball history.
On July 18, the New York Yankees held a 10-game lead in the American League East (h/t Baseball-Reference). At this time, they looked like the best team in baseball.
The Yankees struggled a bit, but they still held a five-game lead in the East and a 6.5-game lead in the wild card a month later (h/t Baseball-Reference).
By Sept. 3, the lead had shrunk to just one game in the division and 2.5 games for the wild card (h/t Baseball-Reference). If the Yankees miss out on the postseason, they will join the ranks of some of the worst stretch-run collapses in MLB history.
Entering Aug. 20, 1995, the California Angels had a 9.5-game lead in the division and a 12-game lead in the wild card (h/t Baseball-Reference). Needless to say, they had to be feeling pretty good about their playoff chances.
In the next two weeks, they saw their division lead fall to 5.5 games and their wild-card lead drop under 10 games (h/t Baseball-Reference). This shouldn't have been a huge cause for concern, as the Angels were still in the driver's seat.
However, the Angels continued to struggle in the month of August and won just 11 games. They ended up in a one-game playoff with the Seattle Mariners. California lost and missed out on the playoffs that year.
Atlanta then won just five of its next 16 games, but still had a shot at a one-game playoff during the last game of the year. It took a lead into the ninth inning against the Philadelphia Phillies, but its reliable closer, Craig Kimbrel, blew the lead.
The Braves would go on to lose the game and their chance at the playoffs.
The American League East is one of the toughest divisions in baseball, but if a team has entered the month of September with a big lead, it can generally hold on to it.
That was not the case for the Boston Red Sox. They were leading the division entering Sept. 1 and had a 9.5-game lead over the Tampa Bay Rays for the wild-card spot (h/t Baseball-Reference). Just 12 days later, the Red Sox had fallen out of first place and saw their wild-card lead shrink to four games (h/t Baseball-Reference).
Entering the last day of the season, the Red Sox and Rays were tied for the wild-card spot. Boston took the lead over the Baltimore Orioles, and the Yankees were up, 7-0, on the Rays in the seventh inning.
Tampa Bay scored six times in the bottom of the eighth. Down to its last out, Dan Johnson came to the plate in the ninth and hit a home run to send the game to extra innings, where the Rays would eventually win.
While that was going on, the Red Sox saw their lead slowly disappear, and the Orioles came back to win the game and knock the Red Sox out of a possible one-game playoff.
New York experienced a September swoon and went just 5-11 over its next 16 games. With a chance to force a one-game playoff, the Mets sent Tom Glavine to the mound against the Florida Marlins.
Glavine got shelled and gave up seven runs in the first inning. There was little fight left in the Mets, and it was clear that their once-promising season was now over.
With a 13-game lead and 51 games left in the season, the Brooklyn Dodgers had to feel fairly comfortable about their playoff chances (h/t Baseball-Reference). They struggled in the second half of August, but still took a six-game lead over the New York Giants into September (h/t Baseball-Reference).
The Giants caught up to the Dodgers, and there was a three-game playoff series to determine who would win the pennant. New York took Game 1, and the Dodgers responded by handily beating the Giants in Game 2.
Brooklyn looked like it had salvaged its season when it took a three-run lead into the ninth inning of Game 3. The Giants scored one after collecting two singles, a pop-out and a double.
Bobby Thompson then stepped to the plate and faced Ralph Branca. Thompson swung at an 0-1 pitch and hit his famous "Shot Heard 'Round the World," giving the Giants the National League pennant.