WATCH: MLB icon David Ortiz shows support for Celtics by sporting Al Horford jersey during Red Sox vs. Braves game

MLB icon David Ortiz was one of Boston's hero during his playing time with the Red Sox, which culminated in 10 All-Star selections and three World Series titles to go along with a World Series MVP in 2013. Also known as 'Big Papi,' the Red Sox legend was in attendance at Fenway Park to promote another Boston based team that is far more near to winning it all than the Red Sox.

Ortiz sported Boston Celtics forward Al Horford's No. 42 jersey in his appearance at the ballpark during the Red Sox vs. Braves game on Tuesday. The Celtics swept the Indiana Pacers in the Eastern Conference Finals to advance into the NBA Finals, where they will be facing the Western Conference champions, the Dallas Mavericks.

With NBA Finals Game 1 slated this Thursday at TD Garden, Big Papi used his presence to gather support for the Celtics. Earlier in the day, Ortiz shared a sneak peek with Larry O'Brien's trophy in his hands, hyping the C's to win the coveted title.

Even during the live broadcast, David Ortiz's support for the Boston team was on full display:

Boston fans have something to look forward to, at least in basketball, where they are just one series away to add to their basketball glory by winning their 18th NBA title and lead for the most NBA championships.

David Ortiz joins Red Sox booth, talks about Celtics chances in NBA Finals

Apart from flashing C's gear, David Ortiz was in the Red Sox booth talking about the Celtics, ready to bring one more Larry O'Brien Trophy to the town.

"They have good chemistry, they are very athletic and they have the tools, they have the play, I mean, you don't see why not," Ortiz when asked about the Celtics chances of lifting the Larry O'Brien Trophy.

"That Indiana Pacers were really fast and they kept them under control, I'm pretty sure the Celtics are good to go. They are ready to win the championship once again."

Over the next two weeks, basketball fans will be thrilled with one of a kind matchups as Jayson Tatum and his team look to take down Luka Doncic's Dallas Mavericks. Expect Big Papi to be there when the game tips off this Thursday at TD Garden.