It's official: The Mets will be without closer Bobby Parnell all season.

Just three days after saying he hoped to avoid Tommy John surgery, Parnell changed his mind on Sunday. The Mets announced Sunday night that he will have the procedure Tuesday.

After suffering a blown save on Opening Day last Monday and pitching with decreased velocity, Parnell complained of forearm tightness to team trainers. An MRI on his elbow the next day revealed a partially torn medial collateral ligament.

Both Parnell and the Mets initially hoped he could avoid surgery by way of a platelet-rich plasma injection, which he had Tuesday, followed by two weeks of rest. The plan was to see how his elbow responded during a subsequent throwing program.

But Parnell also had said that if he was going to need the surgery, he didn't want to prolong matters because of the lengthy rehab. Pitchers typically don't return to the majors for about 12 to 15 months, so he admittedly was concerned about losing too much of next season, too.

Mets medical director Dr. David Altchek will perform the procedure at the Hospital for Special Surgery, the team said.

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The Mets had planned for Parnell to be the linchpin of the bullpen, but that plan carried its own health concerns, considering Parnell was coming off neck surgery last September.

Parnell had two discs fused together, similar to the surgery that Denver Broncos quarterback Peyton Manning had in 2011. He didn't begin his throwing program until later in the offseason, and his spring training schedule was a few weeks behind his fellow relievers.

Once Parnell started appearing in games, his velocity was down, and it never recovered. But the reality is that his velocity has been on a steady decline in recent years, from 97.2 mph in 2011 to 95.0 mph last season. His fastball averaged 92.3 in one inning on Opening Day.

Parnell hopes the elbow surgery will help him regain his velocity and get him back on the mound early next season. He will join Mets pitchers Matt Harvey and Jeremy Hefner, who are rehabbing from Tommy John surgery performed late last year.

In the meantime, the Mets will ride veteran Jose Valverde as their closer and a mix-and-match system in the eighth inning featuring Kyle Farnsworth, Jeurys Familia and lefthander Scott Rice.

Valverde, signed to a minor-league contract with an invitation to spring training, has been effective thus far. His fastball has averaged only 91.7 mph -- down from 95 mph in his heyday -- but he hasn't allowed a run in 3 1/3 innings and has struck out six.