The German mentor, who was hired in December to help the Dube Birds in the fight to retain their DStv Premiership status, quit abruptly to take over at German third division outfit SV Mappen until the end of the season.
Mogashoa revealed that Middendorp’s request to leave came via a letter.
“The coach sent us communication on Monday night requesting to leave his post, but I have not spoken to him since,” the Swallows boss explained.
“Our focus is the remainder of the season, and we trust Musa Nyatama to return to the role of head coach and lead the ship. The players trust him and he has been here from the beginning – he will need our support.”
Pushed for more details on Middendorp, who walked away from a three-year contract in favour of a short term deal in his native country, the chairman insisted that he was yet to follow up with the former Kaizer Chiefs coach.
Nyatama briefly took charge of Swallows earlier this season when coach Dylan Kerr was sacked following a string of poor results and has a record of one win, two draws and one defeat from four league matches.
He also sat on the bench in the opening five games before Kerr got his work permit at the start of the 2022/23 campaign.
The Dube Birds are third from bottom of the table and five points clear of the automatic relegation position with eight fixtures to go.