HOUSTON — The Mets would have been better served had the Phillies retained Gabe Kapler.

Not because he is a bad manager (which he might be), but because it would have meant the Phillies would not be looking for a manager. There already was a lot of competition for candidates, with seven teams trying to fill an opening. But when the Phillies made it eight, that became the most overt competition for the Mets.

That’s because they share so much, from the NL East to their large Northeast market size. But at this moment, nothing is more relevant than that both are in win-now phase having come off of dissatisfying two-year runs with first-time managers: Kapler and Mickey Callaway. It does not mean both teams will hire experienced managers this time around. But it sure appears they’re leaning that way.

That means a Venn diagram overlapping of candidates. And I am thinking particularly of Joe Girardi. The Mets have Girardi on their list of at least five possibilities who will get face-to-face interviews. It would be a shock if the Phillies do not have him on theirs as well.

Besides his credentials, Girardi has a strong relationship with Phillies team president Andy MacPhail, going back to their mutual days with the Cubs. Plus, they were on opposite sides during collective bargaining agreement negotiations when Girardi was still a player — and their mutual respect helped ease some of the tension in talks.

Thus, though the Phillies are getting the latest start when it comes to a managerial search, they need to vet Girardi less than others, including the Mets. So if the Mets have strong feelings about Girardi, then they should prioritize moving decisively.

The Mets have been tight-lipped since firing Callaway. They are trying to limit noise and leaks around the process. Yet, a sense — and it is just a sense — is that someone will have to decisively win the interview process for the Mets’ first choice not to be Girardi. That is because, of the known face-to-face candidates for a win-now team, Girardi is the only one with previous major league managing experience — Carlos Beltran, Mike Bell, Luis Rojas and Derek Shelton have none.

And because the fan base appears to favor Girardi’s candidacy and ownership has historically shown it wants to be popular with the base.

But who knows? No one saw Aaron Boone coming when the Yankees ditched Girardi after the 2017 season because they thought (among other things) there was too much tension projected in Girardi’s day-to-day bearing and in his relationships with the front office, clubhouse and media. If experience is prioritized to try to capitalize on a win-now roster and lack of a farm system, then at least talk to Dusty Baker for his ability to create a positive work environment and Bruce Bochy for his skill at running a bullpen, and think about making Rojas a bench coach and apprentice.

It certainly is possible for the Mets to surprise. They shunned convention and expectations last year by hiring an agent, Brodie Van Wagenen, who has demonstrated he is not averse to making a zig when the expectation is to zag — for example, buying at the trade deadline with Marcus Stroman rather than selling.

A few months ago, the zag would have been to a veteran, recycled manager since the trend in the game was younger, less expensive and more subservient to baseball operations. Now, though, what’s old is new again. It will be shocking if Joe Maddon does not get the Angels’ opening and Mike Matheny that of the Royals. Buck Showalter is at least in interview mode and could wind up with the Phillies, since he too has strong ties to MacPhail and is a plug-and-play, win-now manager.

And there is that scenario in which Girardi could end up a front-runner in Philadelphia and New York. If this plays out, then the Mets should expect Girardi to maximize his leverage.

After Joe Torre was dismissed in 2007, Girardi called being the Yankees’ manager his “dream job” while he continued to negotiate with the Dodgers to push the Yankees to pay him more. When Girardi’s contract was expiring in 2013, there were lots of plants that he could abandon the Yankees for the Cubs.

Look, there are no sure things right now. This is managerial free agency, and Girardi may be in big favor in multiple places or get no job whatsoever.

But if the Mets strongly believe already that he is the right guy, then this would be the moment to at least try to keep a division rival out of the process. Second rounds of interviews are nice. Having your first choice is better.