The forward joined on loan for the rest of the season from Manchester United on Sunday, with a £40m option to buy.
Rashford, who has not played since December, has been criticised by United manager Ruben Amorim, with the Portuguese saying he could not get him to see his way of thinking.
The 27-year-old, who has scored seven goals in 24 games for United this season, has trained well this week and could be in the squad to face Tottenham Hotspur in the FA Cup fourth round at Villa Park on Sunday (17:35 GMT).
“My challenge with him is a huge challenge. His challenge with us is exciting,” said Emery.
“I don’t want to know the reason he is leaving from Manchester but I am very happy keeping him here and I am very happy to try to exploit and help him recover his performances, individually and collectively.
“The conversation I had with him was a very normal conversation with a player and coach, speaking about football. I only want the best football from him.
“I think he has huge potential to exploit.”
Rashford was signed in the transfer window alongside Marco Asensio, Axel Disasi, Donyell Malen and Andres Garcia, but forward Malen and defender Garcia have been left out of Villa’s Champions League squad.
The club could only register an extra three players for the knockout stage under Uefa rules, meaning Malen, who arrived from Borussia Dortmund, and Garcia from Levante, are omitted.
Emery said: “The rules only can register three changes. We did more changes in the transfer window than we wanted and even we lost one player more in the list because Jaden Philogene [who joined Ipswich] was a club-trained player and we lost the possibly through him to have one more.
“We changed five players and only we can register three.
The decision we had to take and they are out, Andres Garcia and Donyell Malen.
“It was not a good decision but I spoke with Andres and Donyell to tell them the decision and I argued my decision with them.”
Villa will be without striker Ollie Watkins against Spurs after he sustained a groin injury in Saturday’s 2-0 defeat at Wolves, while Chelsea loanee Disasi is cup-tied.
“For him [Watkins] each day it is important how he is feeling. For Sunday he’s not going to be available because today he didn’t train and tomorrow he won’t train as well,” added Emery.
