David Ortiz was the greatest designated hitter in the history of baseball, and his contributions to the Red Sox turned around the franchise's fortunes.
Ortiz spent the first 6 years of his career with the Minnesota Twins, where he was splitting time between the minors and the majors. Just when he was starting to show some promise, the Twins released him, and he signed a single-season deal with the Red Sox that was guaranteed only if he made the team.
He made the team, but hardly played in the first two months of the season, until he was finally given the chance to be the team's regular DH, and he responded with a .288 average, 31 home runs, and 101 RBI, which got him fifth place in the AL MVP voting and a new contract.
In 2004, he finished second in the league in both home runs and RBI, and he and Manny Ramirez became the first pair of AL teammates in 73 years to bat .300, hit 40 home runs, and reach 100 RBI, the previous pair being Babe Ruth and Lou Gehrig. In that season's playoffs, the Red Sox went down 3-0 to the Yankees, but battled back to win the series behind Ortiz's brilliance, specifically game-winning hits in extra innings in games 4 and 5. He was awarded the ALCS MVP after batting .387 with 11 RBI in the series, and the Red Sox won their first World Series in over 80 years just weeks later.
In 2005 he led the league in RBI's with 148 and set a new career high with 47 home runs, finishing second in the MVP voting to Alex Rodriguez. The next year, he was easily the best batter in the AL, leading the league with 54 home runs, 137 RBI, and 119 walks, but only finished #3 in the MVP voting after the Red Sox missed the playoffs.
He had another great year in 2007, leading the league in walks again and setting his career high with a .332 average. The Red Sox returned to the World Series that year, with Ortiz batting .714 in the ALDS, and they again swept the World Series, this time over the Rockies, earning Big Papi his second championship.
For the next few years he struggled after sustaining a wrist injury and an Achilles injury, and people started to wonder if his career might be over. However, in 2013, he showed some signs of his previous greatness, and the Red Sox reached the World Series again. This time, Ortiz totally dominated the Cardinals, batting .688 with 6 RBI, and he tied the World Series record by reaching base 9 times in a row, all of which earned him the World Series MVP and his third title.
Late in the 2015 season, Ortiz hit his 500th home run, and shortly thereafter announced that he would play one final season before retiring. That final season was a memorable one, as he led the league with 48 doubles and 127 RBI, which was a fitting end to a great career.
Ortiz is one of only 4 players in history with 500 home runs and 600 doubles, along with Barry Bonds, Hank Aaron, and Albert Pujols. He also hit more home runs (38) in his final season than any other player in history, and hold the career record for World Series batting average, at .455. Even with the slow start to his career, he ended up as the best DH ever, and he was absolutely amazing in each of Boston's 3 championship runs during his time there, which makes him an easy choice to be a part of the top 50 players of all time.