On this, the most optimistic day of the baseball calendar, what’s your most encouraging Mets sign?

The shiny new manager?

The relatively healthy starting rotation?

Sandy Alderson’s bin full of winter bargains?

Well, ladies and gentlemen, we have a late entry into the field: Yoenis Cespedes is fired up.

Upon concluding the team’s pre-Opening Day workout at a chilly Citi Field, the Mets’ highest-paid player — wearing a sleeveless T-shirt — surprised veteran observers here by 1) participating in a news conference; 2) speaking English and 3) offering brash words in support of these 2018 Mets, who launch their redemption effort Thursday at home against the Cardinals.

“I’ve been so far on 14 different teams, and for me, this team, this year is the best team that I’ve been around,” Cespedes said while sitting alongside Todd Frazier and Jay Bruce. “So I’m really excited to go outside [Thursday] with this team, with the fans. I think we have a [good] chance this year because this team, for me, is way better than the team we had in 2015, and we went to the World Series. I think we are ready to go.”

Whoa! Where did that come from? While Cespedes can be engaging and entertaining in one-on-one conversations, he typically offers little of note in group-interview settings like this one.

Is he right? You could argue this team breaks camp with more talent on the major-league roster than did the ’15 Mets. You also could contend that club’s deep farm system provided both in-season reinforcements and trade chips that this group just won’t have.

That debate will be resolved in due time. The more fascinating component Wednesday was just how content and relaxed Cespedes looked during both the practice and the news conference.

Sitting down next to Frazier, upon receiving his first question, he started, “I’m gonna try in English today.” It marked his first time speaking English in such a session since joining the Mets, something which should appease the dolts who whine when Latino athletes use interpreters. And he should feel awfully good about his first foray.

Asked about first-year skipper Mickey Callaway, Cespedes said, “I think Mickey, what I can see so far, he’s got a chance. For me, the best thing is he’s really young. He thinks more the way we think, the players. I think that’s a big point.”

Terry Collins, who already ranked behind Bob Melvin on Cespedes’ all-time manager list, probably won’t be thrilled to read that.

Concerning Callaway hitting him second in Thursday’s lineup Cespedes said, “I think that last year they got someone who said the best hitter, they put him second. Mickey told me that. So I say, if that is what I have to do for the team, if that’s going to be the best for the team, I’ll do that.”

And when a reporter followed up on what Cespedes saw to rank this club as the best on which he has played, Cespedes said, “Everything. The pitchers, the bullpen, the infield, the outfield, I think the hitters. I think this year, we had some guys hurt in spring training, but right now, everybody’s healthy except [Michael] Conforto and he’ll miss I think five games. That’s why I see this team as the best team I’ve been around so far.”

Fair enough. Again: We’ll find out whether he’s right. On this day, his enthusiasm, rather than his forecasting prowess, stood out the most.

A happy and engaged Cespedes, who does not always act that way, can significantly boost Callaway’s initiative to rebuild the winning culture that got wiped out by last year’s flurry of injuries and ineptitude. Cespedes, remember, played a huge role in making that ’15 team what it was with his enticing mixture of on-field bravado and athleticism.

Throwing some off-field bravado into that cocktail can’t hurt, right? Time to think big and play ball. If Cespedes can do the latter as well as the former, the Mets might just get the renaissance they want — and need — so badly.