Linfield boss David Healy admitted he was relieved to finally see off Ballinamallard United following a "chaotic" finish to Tuesday night's BetMcLean League Cup tie.
The Blues emerged with a 5-4 victory at Ferney Park after the first round clash went to extra time.
The holders trailed 1-0 and then 3-2 to the Championship underdogs before Daniel Reynolds levelled in the 88th minute.
A Ben McCann own goal and an Andrew Waterworth strike then eased Linfield into a 5-3 lead, with Sean McEvoy netting a late consolation for the Mallards.
Linfield will travel to Stangmore Park to face Dungannon Swifts in the last-16 of the competition on October 8.
"It turned into a little bit of chaos towards the end," Healy said.
"Even at the end of extra time when I thought we would finally see it through at 5-3, we concede in the 120th minute.
"I am disappointed, overall. But I suppose cup football is all about getting into the next round.
"We can, and we will, play a lot better. Credit to Ballinamallard for making it difficult for us. They played with a solid back five which made it difficult.
"But my players went right to the end, and we ended up going with a formation of 2-3-5 at one stage, it was bodies everywhere. We got (Matthew) Shevlin on, (Daniel) Reynolds on, and Daniel popped up with an important equaliser for us to keep us in the tie.
"We adjusted in extra-time, but we had so many attackers on. But they did adjust.
"All in all, I am relieved, pleased and delighted to get through and book a tie against Dungannon in the next round."
Linfield were pushed right to the wire by Harry McConkey's Ballinamallard, who reached the final of the Irish Cup last season.
Healy praised the character of his players in getting the job done, but insists they will need to improve for next week's trip to Carrick Rangers in the Premiership.
"We could have nicked a winner and saved ourselves an extra 30 minutes, but I can't criticise the attitude of the players too much," he said.
"It is the first round and we have made it through. We are still in the competition."
He added: "We have more levels to go and more in the tank and we will improve. But we can't leave it to the stage like we did tonight.
"Niall Currie (Carrick boss) sets his team up with a back three or back five, so we will need to be better next week.
"The players are disappointed in there. Individually and collectively.
"But, me trying to be positive at the end, I told them it is never going to be plain sailing all the time.
"Sometimes you need to be lucky and you ride your luck, especially in cup competitions.
"You have to find a way to win, and the players did that tonight."
Meanwhile, Mallards boss McConkey praised the effort of his players following a mammoth effort in the tie.
"We never thought we would be in the position of leading with two minutes to go and it was unfortunate for us in the end," he said.
"It was a great game for our supporters and we scored some great goals against a very strong team so hopefully our players will take a lot of confidence from the game."
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