It was 17 years ago this month, in David Ortiz’s first season with the Red Sox, that everything started to change for him -- and for the Red Sox. Ortiz was batting .200 at the start of May 2003, .247 by the middle of the month and up to .272 by the end. It meant he had started to hit, and wouldn't stop until he retired after the '16 season. He was about to change baseball history the way an old Red Sox player named Babe Ruth did after leaving Boston for the Yankees.

“This is our ... city,” Ortiz famously said one Saturday afternoon at Fenway Park, with a famous expletive in there, too. It was the Red Sox's first home game after the Boston Marathon bombing in 2013. His words became a rallying cry for his team and his city as the Red Sox were on their way to the third of their four World Series titles in this century. It would be Ortiz’s last World Series with the club. The Red Sox's record in the ones he played was a mere 12-2.

It was his city in baseball. He wasn’t the best hitter the Red Sox ever had, that title will always belong to Ted Williams, the last man to hit .400 and the best pure hitter who ever lived.

But no hitter and no player has ever been more important to the Boston Red Sox than David Ortiz was. He was a baseball legend once released by the Twins the way Johnny Unitas was released by the Pittsburgh Steelers before becoming a football legend with the Baltimore Colts. The Red Sox hadn’t won a World Series since 1918 before Ortiz got to town. You know what they have done since. He may not be the best hitter in Red Sox history. As a DH almost exclusively, but of course not the all-around player that the great Carl Yastrzemski was, or Mookie Betts. Ortiz is just the most important player the Sox have ever had, because of what he did and what the Red Sox have done in this century.

We have looked back at a lot of the players and moments and teams in baseball history that have always made baseball’s place in the country’s sports landscape feel both as meaningful and essential as it has. All this has been done in anticipation of what will feel like the most meaningful season in all of baseball history if it starts up again in July. Today it’s worth taking another look at Papi, the guy who did the most to end the Curse of the Bambino, mostly because he had so much Bambino in himself. And who became Boston's “Mr. October” along the way.

It all really began at exactly this point in the baseball calendar of 2003. There are so many fascinating parts of Ortiz’s story, starting with this: He didn’t officially become a regular with the Red Sox in ’03 until May 29 of that year. Here is something Ortiz’s agent Fernando Cuza once said to my friend Howard Bryant for an oral history about Ortiz for espn.com:

“When David got in the lineup, you could see the change. He played like he knew he was never going to be in that position of being so close again. I think every professional athlete has a turning point in their career. This was his.”

And after he made the turn, Ortiz never looked back. Over the last three months of the 2003 season, Ortiz hit 27 home runs and 101 RBIs, and ended up fifth in the American League MVP Award voting. The Red Sox went to Game 7 of the AL Championship Series and had the lead in the 8th inning before manager Grady Little left Ortiz’s friend Pedro Martinez in the game too long. The Yankees tied the Sox, then beat them in the bottom of the 11th inning when Aaron Boone won the pennant with a home run off Tim Wakefield.

Then came 2004. Then came the ALCS against the Yankees, when Ortiz and the Red Sox pulled off the greatest comeback of them all after being down 3-0. Ortiz had already hit .545 in a Division Series against the Angels that year. Against the Yankees, he hit .387 with three home runs and 11 RBIs. In Game 4, he won the game in extra innings with a home run off Paul Quantrill to keep the Red Sox alive. The next night, extra innings again, he knocked in Johnny Damon with a single. Now the Yankees only led three games to two. You know what happened in Games 6 and 7. Then the Red Sox went on to sweep the Cardinals in the World Series. Curse over. Because of a new Bambino.

When the Red Sox won again in 2007, Ortiz began October by hitting .714 as the Red Sox were sweeping a Division Series from the Angels. Ortiz ended up with 10 postseason RBIs that year, one that ended with another World Series sweep, against the Rockies.

In 2013 -- the Boston Strong year because of the Marathon bombing -- Ortiz saved the Red Sox from going down 2-0 at home to the Tigers in the ALCS with a game-tying grand slam in Game 2 off Tigers closer Joaquin Benoit. The Red Sox won that night and never looked back. They once again met the Cardinals in the World Series. In that one, Ortiz was as dominant a presence at the plate as anyone in baseball history: He hit .688 against the Cards in six games with two homers, six RBIs, an OPS of nearly 2.000 (1.948) and an on-base percentage of .760.

Ortiz would hit 17 career postseason home runs for the Red Sox. He would hit 483 regular-season home runs. Again: We’ve talked about so many great players while waiting for baseball. So many great moments. No one made more October moments than Papi. No player in this century meant more to his team than he did. Ortiz changed history, changed everything for the Red Sox. And it all started in late May of 2003.