Before the Celtics’ season even ended last spring, the top of their leadership was already thinking about making some changes.

Celtics co-owner Wyc Grousbeck was sitting courtside at TD Garden as he watched his team getting blown out by the Heat in Game 7 of the Eastern Conference Finals. His thoughts about the future quickly began running through his mind.

“I sat there probably the whole second half of that game starting to think about it,” Grousbeck said Wednesday in an appearance on WEEI’s ‘The Greg Hill Show.’ “And then I took two days to let everything settle down and then went and met with Brad Stevens and Joe Mazzulla, and we formulated a plan. …

I just said, ‘We’re not bringing back the same team.’ It’s been two seasons in a row of really good play but inconsistencies and they showed in the Finals two years ago and then in the conference finals last year. It just felt inconsistent and I said, I just want to change the mix so that there’s just a freshness, a fresh approach, so we made some changes this summer.”

About three weeks later, the Celtics did just that. They shockingly traded beloved point guard Marcus Smart and landed Kristaps Porzingis. Then, on the eve of training camp, they swung a deal for Jrue Holiday.

The mix was successfully changed as they assembled arguably the most talented roster in the league. The Celtics entered the season Wednesday as co-favorites with the Bucks to win the championship. Expectations, as usual, are high in Boston. But Grousbeck cautioned against it being championship or bust.

“It’s the ‘or bust’ part because I don’t think it’s a one and done, like it’s now or never,” Grousbeck said. “I said in another press conference earlier, I think we might have a six-year run here. I just pulled that number out of the air, but our two really marquee players, now we have four or five or six really top players. We have a top six that’s unbelievable. But Jaylen (Brown) and Jayson (Tatum) are in their mid-20s. Jaylen just re-upped for a long contract and we have the opportunity to talk to Jayson next summer and hopefully extend him. Having them in their mid-20s means that I’m looking at this as a period where we can be good every single year. …

“I’ll be so disappointed if we don’t do really well this year and give it a good try, give it a good fight, but I don’t think it’s now or never.”