Jonsson was suspended for the 2-0 defeat by Motherwell after his controversial sending-off against Rangers but his weekend improved dramatically on Sunday when he received the club's young player of the year award.
The 21-year-old is almost certain to come back into the starting line-up for the Clydesdale Bank Premier League clash against Hibernian at Easter Road after Hearts lost limply without him.
Jefferies told Hearts TV: "Eggert fully merited the award. His attitude and determination is an example for others at the club. He trains every day like he plays at the weekend and because of that, it makes it easier for him to perform on the park.
"I knew he was a good player before I came to the club but I've now seen at first hand what a terrific professional he is."