O'Brien performed admirably at right back following a spell in the opposite full back position and the Republic of Ireland international was delighted to keep a first clean sheet in ten attempts.
"We haven't been on it defensively lately," he told West Ham TV. "At the start of the season we were doing some good stuff at the back, but we had gone off the boil and were giving easy goals away.
"So it was great to get back with a clean sheet against Swansea. That's the first thing you have to get right - the manager said that just before the game, make sure we come in with a clean sheet.
"That's what we wanted and we got the result, which was massive for us.
"It was grand at right back. I've played there quite a lot, and although I've been at left back too it's not that big a deal for me to go to the other side."