Frustration has reached boiling point

SAN FRANCISCO — Terry Collins raised his voice, and that alone told you the severity of the situation. Collins has kept his cool for most of his tenure as Mets manager.

On yet another crazy day with the failing Mets, Asdrubal Cabrera, who was starting at second base Friday night against the Giants at AT&T Park, proclaimed before the game he wants to be traded as quickly as possible because he still considers himself a shortstop.

“He’ll be playing second base tonight, I know he is not happy about it, I just found out so we are going to move on,’’ Collins said. “It’s over.’’

When another question started to be asked about the situation, Collins nearly blew a gasket. “We’re going to move on,’’ he said loudly. “We’re moving on. What’s next?’’

Welcome to Collins’ world, in what could be his last season as Mets manager. Managing players on a losing team when the for sale sign has been planted by general manager Sandy Alderson is not easy.

This could be some farewell tour.

Collins quickly calmed down when The Post asked the question: What if another player comes in and asks to be traded?

“It’s always a new challenge,’’ he said. “That’s why this is not an easy job.’’

No it’s not, and now it’s much more difficult.

“There was a discussion and I made a decision,’’ Collins said. “This may be the first time I’ve had something like this occur. We’ll get through it. Right now everybody needs to look in the mirror and do their jobs.’’

Collins has had to put up with many obstacles during his managerial career with the Mets. Now comes one of the most difficult.

“I tell the players you can always control what you can control,’’ Collins said. “It can be hard, but I try to go back to where my communicative skills with my players, where in my opinion, has created an atmosphere here, a positive atmosphere and that will not change.

“I’ve talked to several guys and when you have the number of free agents that we have that are all worried about things, I have addressed it with everyone of them.”

Reality finally slapped the Mets in the face in Los Angeles, but this has been coming for a while. This Mets team was headed to trouble with all the injuries. Now the Mets are hopeful of making deals on various veteran players in the hopes of bringing something back for the future. It finally has dawned on them they have to get younger and more athletic. It would be nice if they got more talented, too, but we will have to wait to see how it all shakes out.

The challenge for Collins, 68, is to somehow make this all work. In the last year of his contract, in the midst of a Mets reign that began in 2011, Collins will have to face the cloud of trade rumors for five more weeks and try to keep his team competitive and engaged. Good luck with all that. The Mets got bashed in L.A., losing all four games to the Dodgers and allowing a record 15 home runs. They had lost seven of eight games since Alderson proclaimed they have good players — maybe he meant good players to trade.

The Mets have to improve defensively. This has been a nightmare trip on defense for the Mets with critical errors made by the infield. All this has been weighing heavily on Collins, a baseball lifer.

No matter what happens with the Mets, Collins has told friends he still wants to stay involved in the game in a meaningful way next season. Baseball is in his blood. He needs to be in the game.

After days like Friday, and this entire week, the challenge of managing these Mets grows much more difficult by the day.

One thing is certain: It is not going to be easy for Collins and his Mets to move on in this atmosphere.