To say Isaiah Thomas didn't take his trade from the Boston Celtics well would be an understatement, with the All-Star guard feeling blindsided by the franchise. 

Thomas spent the past three seasons as a member of the Celtics, helping the franchise turn around after a dismal 25-win season. Boston made the playoffs in each of Thomas' three seasons with the team, and Thomas is coming off a career year.

When you average 28.9 points for a team that just made it to the Eastern Conference Finals, it's hard to envision being traded months later. The situation led to an outpour of messages from fellow NBA players, athletes, celebrities, friends and family. One message stuck out to Thomas, though.

Thomas wrote a revealing and personal letter on The Players' Tribune, explaining exactly why the trade hurt him so much. He explains how he envisioned himself cementing himself alongside other greats who've elevated one of the most historical franchise in all professional sports, hoping to be whispered with the likes of Paul Pierce, Larry Bird and Bill Russell. 

Instead, his career with the Celtics was cut short, robbing him of that expectation. That's why, when another Boston sports legend reached out to him, it stung just a little more. Thomas revealed a text message exchange with New England Patriots star Tom Brady stuck out to him. 

"What’s up, IT, I heard about the news. You good?

I’m alright. I mean, it’s crazy. It’s a cold game.

Yes it is. Best of luck. You’re gonna do great. Keep in touch," the exchange went, as Thomas wrote in The Players' Tribune. 

As for the why it was a bittersweet moment, Thomas explained his mindset.

"At first, honestly, it stung a little. I look at a career like Tom’s with the Patriots — and that’s exactly the kind of career that I had hoped to be building here with the Celtics: Being this low draft pick … coming in without acclaim … and then — through hard work, and determination, and some talent that maybe people had overlooked — just starting to win, and win, and win.

"And then establishing a legacy of winning. And then staying in Boston, winning titles and competing like hell, for the rest of my career — until I was considered one of the all-time Boston greats. That’s the career that I had started to map out for myself," Thomas said.

It's clear Thomas was all in for the Celtics, wanting to be a part of a tradition matched by few. His three-year run, along with his career-year and gutsy final playoff run with the franchise, won't soon be forgotten by Boston fans though.