Sali joined Chippa in 2010, and despite a short stint at Polokwane City during the 2013/2014 season, he still became the Chilli Boys' longest serving midfielder.
"The process to renew Sali's contract started last year," Mpengesi said.
"As the football club we did all [that was] possible to keep the player at Nelson Mandela Bay Stadium. Negotiations have completely broken down and the player will depart at the end of the season."
Mpengesi though took time to wish Sali well for the future.
"Chippa United in its entirety would like to express a word of gratitude to Buyani Sali for the contribution he has made to this football club. Sali has been a key player for the club since our days at Vodacom League [now ABC Motsepe League) and when the history of this football club is written the name Buyani Sali will be there. We are delighted to have given him a platform to show South Africa what he can do on the pitch.
"We wish him all the best in his endeavours," concluded Mpengesi.
Meanwhile, the club have moved swiftly to fill the void left by Sali in midfield, announcing the signing of Boikanyo Komane (25) from Royal Eagles and Ntuxeko Nation Ndlovu from Cape Town All Stars.
Exciting forward Lucky Setelele from All Stars has also signed on the dotted line to increase the firepower upfront.