When Aidan Dunleavy calmly clipped the ball over the head of the advancing Jack Jenson to put Manulla 3-0 up after 29 minutes - it looked like his side could win this game by five or six or even more.
The hosts were already stretching the limits of their squad depth before this game began but before half time they lost Stephen Walsh, Liam Whyte and captain Ioseph O’Reilly to injury further adding to their woes.
But while Manulla always looked like they were going to win this game, Jordan Loftus' deft header just before the break - gave Celtic a chance and the knowledge that another goal would really throw the cat among the pigeons. But they were unable to prize open the visitors defence in the second half, despite repeatedly knocking at its door.
Jordan Loftus had a half chance to put Celtic into the lead inside the first minute but his header from Jason Hunt’s cross flew over the bar.
A minute later the first goal of the day came when Gerry Canvan sweetly finished to the net. The visitors doubled their lead five minutes on when Canavan found David McCracken who played in Lorcan Conroy and the left back made no mistake with his effort and his side were 2-0 up.
Further chances presented themselves to Canavan and Shay Benson and there was even a penalty given to Manulla that was overturned following advice from the linesman - the first of two such incidents to happen during the game oddly enough.
Dunleavy was picked out for his goal by a raking pass from Chris Maughan just before the half-hour and Celtic were all at sea and taking on serious water.
But they did battle back and Loftus nipped in before the break to cut the gap to two goals heading into the second 45 minutes.
For long periods of the second half, Celtic prodded and poked around the Manulla defence but they were’t able to create the spaces they needed to work a goal.
The visitors were happy to sit back, soak up the pressure and hit on the counter attack and one more than one occasion they almost got in for a fourth goal that would have killed the game off.
This was Celtic’s second defeat in four days having lost to Westport United on Thursday night last and they now find their title defence well off the leading sides having lost three of their five league games so far, while it sees Manulla keeping pace with at the top of the table with four wins from five under their belts so far this season.
Castlebar Celtic: J Jenson; R Nevin, I O’Reilly, S Walsh, M Howley; L Whyte, B Walsh, N Douglas, P Walsh; J Hunt; J Loftus. Subs: C McHale, L Hay, G Hunt.
Manulla: A Byrne; J Webb, C Moore, A Shally, L Conroy; A Dunleavy, C Maughan, C Byrne, D McCracken; G Canavan, S Benson. Subs: E McGahon, A Brennan.