Gabriel's comments came after Mhango netted his fourth goal of the campaign in a 1-1 draw against Sekhukhune United in a midweek Betway Premiership clash at the New Peter Mokaba Stadium in Polokwane.
Mhango, who joined Richards Bay after a spell with Marumo Gallants, has quickly become a central figure in the squad.
The 33-year-old is also in excellent form internationally, having scored twice for Malawi during the September FIFA international break.
"We think he has made fantastic progress so far; he has been influential," Gabriel told FarPost.
"We brought him in to score goals, and he's done exactly that. But what's been equally important is the leadership he's shown — guiding the younger players and setting the standard for professionalism at this level."
Gabriel emphasised Mhango's positive effect on the club's youthful squad.
"As you know, we have a lot of young players, and that type of influence rubs off on them. There's been a real sense of belief and positive energy within the group," he added.
The result against Sekhukhune lifted Richards Bay to 11th place on the log, a steady improvement from their early season struggles.
"We must commend the group for their hard work and determination to come back from a goal down against a strong Sekhukhune side," Gabriel said.
"They dominated possession and created chances, but our response showed character. After the equaliser, the game could have gone either way — and that's the kind of fighting spirit we want to build on."
Gabriel will be hoping the experienced forward continues with his good form when they take on Orlando Pirates in the semi-final of the Carling Knockout at Moses Mabhida Stadium on Saturday.