Northern Ireland striker Lafferty has scored three goals in two League Cup games, including a double in his full home debut at Tynecastle on Saturday.
And MacPhee reckons that is the start of something special.
"This is not always an easy place to play but he has the personality to take on the responsibility," he said.
Lafferty joined the Jambos in the summer after leaving Norwich, with the striker having been at Rangers from 2008-12.
The 29-year-old scored last week against Elgin City and took his League Cup tally to three goals with his double against East Fife on Saturday.
And MacPhee reckons Lafferty is set to have a major impact for the Gorgie men this term.
"It was a good win and it was great to see Kyle score a couple on his Tynecastle debut," he added.
"Kyle backs his own horse. He's not afraid to miss a chance and then go back for another one. People might suggest Kyle hasn't scored many goals in recent years - but teams haven't played him. Norwich didn't play him.
"Northern Ireland have played him and he has scored goals, and I believe that will be the case here at Hearts too.
"He will be a massive player for us this season and it's great he's got a few early goals."
Assistant head coach Austin MacPhee believes Kyle Lafferty has the perfect mental make-up to lead the line for Hearts.