Big stage experience the biggest factor for Celtics

There's a calmness that the Boston Celtics seem to be playing with right now. It's a vibe that comes through even when the players speak. 

Following their series-clinching Game 5 victory over the Orlando Magic last week, Jayson Tatum talked about being carefree and having fun playing basketball this season. 

"This season was like the most relaxed and carefree that I've been in my career," Tatum said. "Understanding that we won last year and we accomplished the ultimate goal. You kind of got that monkey off your back." 

As the Celtics start their second-round series against the New York Knicks on Monday at 7:00 p.m. ET, it's hard to deny the big advantage they have over the remaining Eastern Conference field. Boston has reached heights the Knicks, Cleveland Cavaliers and Indiana Pacers are still chasing. The journey the defending champions have taken over the years is hard to duplicate. 

Tatum and Jaylen Brown are the perfect examples of this. If it feels like they've been around forever, well, that's because the All-Star duo has battled dating back to 2017. The 28-year-old Brown has played in six Eastern Conference Finals, while Tatum has five on his resume at the age of 27. Brown has played in 129 playoff games while Tatum has totaled 117. 

They took the usual required steps to reach the top. These steps included battling legends in their prime with the likes of LeBron James and Steph Curry. They've experienced a first-round exit and multiple conference finals losses. They know what it feels like to fall a couple of games short of finals glory. This Celtics group felt the pressure of winning banner 18 before getting it done last year. 

With experience comes confidence in pressure-filled moments. It also brings an innate ability to pivot whenever and however. The Celtics are quick to let it fly from the three-point line but the Magic gave them a physical challenge. Even with injuries to Tatum, Brown and Jrue Holiday (and Kristaps Porzingis bleeding from his forehead), Boston didn't waver mentally. It figured out a way to quickly take away hope from a young Magic squad. 

The Cavaliers finished with the best record in the East, but they still have to prove that the playoff lights aren't too bright. The Pacers beat Cleveland 121-112 Sunday, taking a 1-0 series lead. Indiana got swept by Boston in the conference finals last season. Meanwhile, New York has lost in the second round in the last two seasons. 

These are talented teams with quality players who are capable of taking over stretches of games. Only one of the four left in the east, though, has that undeniable edge. The Celtics have done it before. This is the mental barrier the rest of the field will have to hurdle.