Essendon's disastrous year hit a new low a fortnight ago, with the revelation that skipper Merrett had met with Hawthorn coach Sam Mitchell about a potential move.
The Bombers have been adamant since that Merrett, who is contracted, will not be traded.
There was some good news on Tuesday, with contracted defender Jordan Ridley saying he would no longer seek a trade to Brisbane.
"Zachy - he's an extreme competitor, he wants to win, he wants to get the absolute most out of his career and he has been an unbelievable servant for Essendon," said Heppell, who preceded Merrett as Bombers captain.
"He's gone to have a conversation with another club - yes, a big rival ... look, he's pursuing the highest and the best thing for him.
"I hope he still stays with the footy club. He's an incredible Essendon person and we'll see how it all lands."
Hird noted Merrett was about to win his sixth club best and fairest award and has been building one of the great Essendon playing careers.
After captaining the Bombers, Hird coached Merrett before resigning in  2015 and is now a media commentator.
"I really hope Zach stays at the club," Hird said. "If he stays that long, he'll probably have the most bests and fairests at the club.
"But as well we all know, that's not why you play - you play for team success and I hope he stays and the club can get its stuff right on-field, and they can have that team success."
Hawthorn are one of Essendon's main rivals and Mitchell will forever be a villain among Bombers fans.
He taunted Essendon players by mimicking an injection during a 2015 game, referencing the club's drugs debacle.
At Monday night's Brownlow Medal count, Merrett spoke of the fall-out from his meeting with Mitchell.
"There's still things I need to work on to see where I end up," Merrett told the Seven Network.
"It's a bit of a shame at the moment, I am not there to upset (Essendon) fans, I appreciate them dearly."
As Merrett's future remains unclear, Ridley has confirmed he will stay at Essendon.
Essendon's 2020 best and fairest winner had considered a move to Brisbane after a frustrating run with injury.
"This off-season gave me a crucial opportunity to reflect on a challenging few years with injury. During that time, it became incredibly clear that my future is with Essendon," Ridley said on the club website.
He spoke of his "immense faith" in coach Brad Scott and was encouraged by Mat Inness, the club's new high performance boss.
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