The two teams will face each other once again with a place in the quarter-finals up for grabs.
And Olsson was upbeat after the Swans were held by their Championship hosts.
“We didn't reach the level of performance that we had hoped we would," said the Swedish defender.
“After the break we played a bit better and had a few half-chances.
“We wanted to win of course, but that is a tough place to go and play.
“We kept a clean sheet and that is pleasing. If you don't win a game then you must ensure you keep things solid and stop them from scoring.
“We didn't have that edge to our game, but we took the game to a replay at our place."