The academy product has made a tough start to the season.
The 29-year old has failed to hit top gear so far this season and has found his influence waning generally over the last few years.
MacDonald still sees him as a vital component in the Villains’ escape from the drop and has backed the former England international to step up to the plate.
"Gabby's season has been very stop-start,” said MacDonald, in an interview with avfc.co.uk.
“He's been picking up niggles - and then the injury that's kept him out for the past few weeks until he got back in.
"Gabby is a player this club will need for the rest of the season to start really bringing up big performances… Gabby has a big responsibility. He knows that. He is club captain. He's been at the club all his life.
"This will be hurting Gabby probably more than most because he will not want to be at a football club as big as Aston Villa and get relegated."
Villa’s pacey frontman hasn’t been prolific in recent seasons and will need a drastic turnaround in form if he is to fire his beloved club to safety.
Agbonlahor’s 73 league goals since his breakthrough in 2006 have made him Villa’s record Premier League goalscorer, but finding the net has proved more of an issue in the past few years.
The 2009-10 campaign was the last time his goal tally reached double figures and his failure to start firing this season could prove fatal for the Villains’ hopes of survival.