PHOENIX -- The 30-day maximum period for Bobby Parnell's rehab assignment in the minors is set to expire on Wednesday, so the New York Mets are poised to activate the former closer from the disabled list later this week.

Parnell is due to make one final rehab appearance for Double-A Binghamton before returning to the major-league club, manager Terry Collins said.

Former closer Bobby Parnell, 14 months removed from Tommy John surgery, is due back with the Mets Courtesy of Adam Rubin

Parnell underwent Tommy John surgery on April 8, 2014.

Unlike with Matt Harvey, Parnell's velocity has not returned to pre-surgery levels. Collins said Parnell's fastball sat at 92 mph in his last rehab appearance. That's considerably below his 95.6 mph average during his major-league career.

Collins said he hopes adrenaline from pitching in major-league stadiums will add some oomph, but that is too big a velocity gap to make up via the energy from a crowd.

Parnell has not demonstrated in the minors that he successfully can pitch with the lower velocity, which will require more pinpoint command. In the Binghamton portion of his rehab assignment, he is 0-2 with a 14.21 ERA in seven appearances. He has allowed 11 hits and six walks in 6 1/3 innings against Double-A batters.

Eastern League hitters are batting .407 against Parnell. And although Collins has suggested Double-A fielders do not make all the plays that are routinely executed in the majors, that is still a startling number.

If there were any thought during spring training of Parnell regaining his former closer's role from Jeurys Familia, that's gone. In fact, this may be Parnell's final season with the Amazin's. He is making $3.7 million in 2015 and is eligible for free agency during the upcoming offseason.

Parnell's last major-league appearance came on Opening Day in 2014. It was after that blown save that he underwent the Tommy John surgery.

Parnell is not the only one soon to return from the disabled list. Catcher Travis d'Arnaud and infielder Dilson Herrera had their rehab assignments shifted to Triple-A Las Vegas and should be back with the Mets within the week. Reliever Vic Black might take a little longer, according to Collins, because his control has not been sound in the minors.

Collins noted those players returning should help. Still, the manager added: "We don't need names. We need performance. ... We can't go through a two-week spring training with them. They've got to be ready to help us."