A late own goal by Seb Hines saw Swansea City overcome second-tier side Middlesbrough 1-0 to book their place in the League Cup semi-finals on Wednesday.
A dour match in south Wales seemed destined for extra time until Boro centre-back Hines put the ball through his own goal as he tried to defend a Swansea corner in the 81st minute.
Swansea join Aston Villa and fourth-tier Bradford City in the draw for the last four, with Chelsea due to visit Leeds United in the remaining quarter-final tie on December 19.
Arsenal's shock elimination by Bradford on Tuesday has opened up the competition even further, but neither Swansea nor Middlesbrough seemed willing to take the initiative at the Liberty Stadium.
In a drab first hour, Grant Leadbitter looked like the only player eager to score, but the Middlesbrough midfielder's three efforts at goal each met their equal in Swansea goalkeeper Gerhard Tremmel. Swansea coach Michael Laudrup turned to Luke Moore 10 minutes into the second half and the substitute had a strong penalty appeal waved away soon after coming on when he went down following a challenge by Andre Bikey.
Belatedly the hosts came to life and in the 72nd minute, midfielder Jonathan de Guzman saw a 25-yard free-kick brilliantly tipped onto the crossbar by Middlesbrough goalkeeper Jason Steele. The hosts' pressure eventually told nine minutes from time when Hines inadvertently headed the ball past Steele from De Guzman's left-wing corner.
The 24-year-old came close to atoning for his error in the 88th minute, but after flying in to meet a corner from the Boro left, he could not keep his header down from close range.