Boston Celtics big man Al Horford understands what it's like to leave a city where his career began and grew, and what it's like to return there wearing a different uniform. Horford signed a max contract in the summer prior to the 2016-17 season with the Celtics and now has the first-hand experience visiting a place that was once called home that turned into a rival's abode.

Horford knows all too well and, in lieu of teammate Kyrie Irving's return to Cleveland, recalled what it was like the first time he returned to Atlanta last season.

The Celtics big man was as cool as possible until he began seeing those he knew and standing in the atmosphere he once soaked in is where things started to change as he recalls to A. Sherrod Blakely of NBC Sports Boston via Yahoo Sports.

“That's when it starts getting to you.”

Players are not robots after all, and it's a good indication of the rude awakening that awaits Irving when he returns to Quicken Loans Arena where he has played his entire career. While he now wears green, he'll be surrounded by too many familiar acquaintances to not be affected in some way.

Kyrie Irving has said all of the right things, handled himself in the eyes of the media very well, but he hasn't been tested by the one thing that will be his biggest challenge — returning to the place he once called home. He still hasn't changed his stand yet and continues to carry himself professionally.

“Personally, it's just basketball. Going up there, understanding the legacy that I was a part of, team-wise and individually, just seeing the maturity and the maturation process I went through of coming in as a 19-year-old kid and being in an unbelievable city such as Cleveland, leaving with (a championship) … That's pretty awesome to see that.”

“And also understand what it took to get that, the team that we did it with and the city of course. And moving on to here in Boston. It'll be an adjustment but I'm looking forward to it.”

That has been his stance from the very beginning. He seems so optimistically happy to be in a new environment that it seems out of place to imagine he could genuinely be that happy after leaving a winning situation.

You can expect his teammates to do everything they can to win the game just for him as they are all aware of the situation, and what comes with the territory. In fact teammate, Gordon Hayward is taking notes because, soon enough, he'll also be in the exact same situation when the Celtics visit the Utah Jazz this season.

“It's gonna be a fun atmosphere for sure. A huge game for Kyrie, one I think we're all looking to play our best for him. Not only for the team, but for him too. We know it's a big game for him.”

It's something the Celtics have done once, now twice and soon to be three times.