Reserves even breaking into the Republic of Ireland U-21s side after starring and scoring in the 1985 FIFA World Youth Championship.
With a team consisting of Kenny Dalglish, Ian Rush, Craig Johnston, Ronnie Whelan and the like coupled with the fact that they were at the time the top club side in Europe it became increasingly difficult for Mooney to make a breakthrough playing in the end just one first team game in a Football League Cup tie against Fulham in October 1986.
Even a successful loan spell in 1986 at Wrexham (8 games, 2 goals) only added to Mooney's desperate need for regular first team action.
The next three and a half years were for Mooney a very successful period with his undoubted natural ability attracting the attention of many top flight clubs and the eye of Republic of Ireland boss Jack Charlton.
Was voted 2nd in the clubs cult heroes Although a Republic of Ireland cap eluded him Mooney did in the end earn a move to top flight Sunderland A.F.C.
His time at Sunderland was however a disaster with the club being relegated almost immediately and Mooney managing just 27 appearances (1 goal) in an injury ravaged two years.