O’Carroll was announced as the successor to John McMahon, who left the same role on Christmas Eve.
A former Shrimps player, O’Carroll moved to the Mazuma Stadium as first-team coach following Stephen Robinson’s appointment as manager last summer.
O’Carroll said: “It’s brilliant. I worked well with John when he was here as well, and I wish him all the best for wherever he ends up next.
“From my point of view, I’m excited. I came in with the manager, ultimately came into a system as a first-team coach initially, so for me and I’m sure for the manager, not a whole pile will change from our day-to-day working.
“I’m delighted. It’s a fantastic one for me, a bit of pride to have once been playing here, being first-team coach and now assistant manager, so (I’m) delighted.
“From his (Robinson) point of view, I know what he wants. I’ve worked with him before, so it allows me to have a little bit more influence on things, potentially with staff and with the academy. It puts more responsibility on my door, which is brilliant.
“I can try and drive certain things that he likes and he wants because he doesn’t have the time to do it.
“He’s enough balls in the air trying to get points and look at transfer windows and different things like that, so it allows me to crack on with the other stuff and take a little bit off his plate if possible.”
Robinson added: “I brought Diarmuid to the football club. I knew what he could bring to it, he’s a fantastic coach.
“He’s a brilliant personality around the place, very, very popular among the players, so I think it’s a really good step up for Diarmuid as well and he’ll be a fantastic help to me as he always is.”
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