Having won six Premiership games from six, Quins switched their attentions to round one of the LV=Cup and, despite a raft of changes to rest senior players - including influential former All Black fly-half Nick Evans - the London club again came up trumps.
"I am unbelievably proud of those players," O'Shea said. "Results always tend to colour your overall reaction to a game, but I had already turned to (coaches) John Kingston and Tony Diprose and told them how proud we should all be of the lads, and we were losing at that moment.
"When you consider for example, that we had 19 and 20 year-old locks out there in Sam Twomey and Charlie Matthews up against England forward Nick Kennedy and former All Black Bryn Evans, they did themselves proud.
"We made a number of changes and Irish were a more experienced side than us as a result, but Rory Clegg came in for Nick Evans, played very well and kicked his goals.
"But then he spent extra hours on the training pitch during the week, hours we didn't demand of him, practising his kicking. He's a very young man with a very professional attitude.
"I was also proud of their determination to keep the ball alive after Rory had equalised for 19-19 near the end.
"The easy option would have been to kick to touch and settle for staying unbeaten, but they had the courage to keep pushing for the winning score."
That score came when Seb Stegmann accelerated up the right and managed to find Ollie Lindsay-Hague while being tackled, leaving the England Sevens star to race clear for a score that left Irish dejected and head coach Toby Booth unimpressed.
Booth said: "I am disappointed with our performance overall because we made too many errors and failed to control the contest for long enough.
"We didn't start well and had to fight tooth and nail after the break to get back in the contest.
"I was pleased with that reaction and that effort, but despite doing well in the scrum and getting on top to take the lead, we didn't see the game out.
"The challenge for everyone was whether to go for the draw or the win. We were probably a bit guilty of being greedy in that sense, but I won't criticise players for keeping ball alive and going for victory."
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