Despite Swansea's excellent 3-1 away victory at Liverpool in the last round and Middlesbrough's 1-0 win over rivals Sunderland, both sides appear to have reached the last eight under the radar.
Nevertheless, Tony Mowbray’s side will be keen to take advantage of the Swans’ indifferent recent home record, having won just two of their last eight at the Liberty Stadium.
Middlesbrough, who are yet to even qualify for the play-offs since their relegation from the Premier League in 2008/09, sit third in the Championship just six points adrift of Cardiff although they won just two out of their previous five matches.
Scott McDonald, formerly of Celtic, has scored three in his last three games.
KICK-OFF: Wednesday, 7.45pm
PAST THREE MEETINGS…
Middlesbrough 3 (Emnes, Grounds, Lita) Swansea 4 (Dyer, Sinclair, Williams, Beattie), Championship, February 2011
Swansea 1 (Sinclair) Middlesbrough 0 Championship, November 2010
Middlesbrough 1 (Flood) Swansea 1 (Pintado), Championship, January 2010
Swansea have scored three goals in each of their three fixtures in this cup run: 3-1 at home to Barnsley, 3-2 at Crawley and 3-1 away to Liverpool.
This is the eighth time Middlesbrough have appeared in the quarter finals of the League Cup - they have advanced on five of those occasions.
Boro have been drawn away in the League Cup for the 12th successive time.
This is the Swans’ first appearance in the last eight of the League Cup.
Middlesbrough's League Cup triumph in 2003/04 remains their only major piece of silverware in their 136-year history.
Swanea to win: 1.7
Middlesbrough to win: 5.8
Craig Beattie’s strike in the fourth minute of injury time sealed a remarkable comeback victory for Brendan Rodgers’ men at the Riverside in February last year.
Marvin Emnes, who had been on loan at the Liberty Stadium earlier in the season, struck the opener before Nathan Dyer equalised from close range.
Goals from Jonathan Grounds and Leroy Lita put the hosts 3-1 up before Scott Sinclair’s penalty and Ashley Williams levelled for the Swans.
Middlesbrough were denied a share of the spoils, though, when Beattie’s low strike snatched all three points.
TV: Highlights on BBC1 at 11.15pm on the League Cup Show