Rugby league: Newcomer Hadden handed Ireland call-up
Hadden, who spent the 2013 season with Championship One club Oxford, replaces Warrington back-row forward Simon Grix, who played in the Super League Grand Final earlier this month but has withdrawn from the Ireland squad in order to undergo close-season surgery.
He is the latest high-profile absentee for the Irish, who are also denied the services of Kyle Amor, Shannon McDonnell and Chris Bridge, but Aston says Hadden jumped at the chance to join the camp in Preston.
"When I made the phone call, he could not contain his excitement," Aston said.
"It's a great opportunity for him to mix with the likes of Brett White and Pat Richards."
Aston's 24-man squad came together at the University of Central Lancashire, which will be their base for the tournament, at the weekend and, having opted not to play a warm-up match, will go straight into their potentially crucial clash with the Fijians at Rochdale on Monday week.
"Some of the guys have played 34 or even 38 matches this year and we didn't want to fatigue them," Aston said.
"We're trying to keep them fresh but we're intensifying the training now and we'll go hard against each other.
"We've had two sessions so far and we'll have another eight before our first game. We haven't had the luxury of going to South Africa for a training camp but we're coming together. It's a case of blending individuals into a collective and the group are getting close."
Ireland are in the same group as England and favourites Australia, with three teams to go through to the quarter-finals.