Oxford United have managed to reach half time on level terms away to Sheffield Wednesday, but the hosts have had several chances to break the deadlock at Hillsborough.
The Owls looked intent on hitting the front early on from set pieces, with Tom Lees having a header saved by Sam Clocombe.
Seconds later, Wednesday were again threatening the United backline as Vincent Sasso took aim at goal but narrowly missed the target.
On 17 minutes, Kieran Lee was inches away from putting the home side in front before Alexander MacDonald's effort was blocked at the other end for the visitors, who beat Brentford 4-0 in the last round.
Lee went close again midway through the half, as Slocombe was called into action to keep out the midfielder's strike.
Just before the half-hour mark, Ross Wallace squandered another chance for Wednesday from a free kick after his shot failed to test the Oxford stopper.
Lee looked the most likely to score for the home side before the interval, but struck another effort wide as the U's survived the opening period unscathed.
