Arsenal boss Unai Emery praised the tactical nous of his opposite number Terry McPhillips after his Premier League giants just squeezed past Blackpool in the Carabao Cup.
The home side went ahead in the 34th minute as Stephan Lichtsteiner poked home Matteo Guendouzi's sublime chip over Blackpool's defence.
Emile Smith Rowe made it 2-0 in the 50th minute as he bundled home Carl Jenkinson's cross.
But then Guendouzi was sent off for a second yellow after fouling Jordan Thompson.
Blackpool were galvanised by the sending off, O'Connor marking his return to the starting line-up with a goal as he nodded home Thompson's corner in the 66th minute.
Blackpool pressed for a leveller but their hopes of a fight back were dashed when O'Connor was sent off for a challenge on Pierre-Emerick Aubameyang.
Emery said: "They are a very organised team, tactically very well worked.
"It was very difficult to win against them, they have players with quality.
"I spoke before the match with (assistant) Steve Bould. He knows the level of this team and said to me it would be difficult.
"I know this team eight years ago were playing in the Premier League.
"We needed a performance and also a big preparation."