The Shadow Line actor and lifelong United fan was asked to interview Rooney by ITV1 ahead of tonight's Champions' League final tie with Barcelona.
Speaking to ITV, Eccleston said: "He walked in looking supremely relaxed, confident about Saturday [and] radiating health... I think he's primed for a big game."
The former Doctor Who star continued by describing the experience as "one of the best days of my life".
"I meet actors all the time and they don't turn my head," he explained. "But to meet a professional footballer of Wayne's calibre - it was one of the best experiences I've ever had."
Eccleston added that he was impressed by Rooney's composure during the interview.
"For him to handle questions with such ease was very impressive," he said.
Eccleston's interview with Rooney will be available on ITV's official website from 7pm this evening (May 28). Coverage of the Champions' League final will begin at the same time on ITV1.
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