The Tottenham Hotspur duo are confident ahead of their trip to Bramall Lane.
Spurs only just beat Nigel Clough's resilient side at White Hart Lane thanks to a Townsend penalty in the second half.
But the Tottenham man feels the second leg could be much more favourable to the visitors, as the Premier League outfit will enjoy more chances duo to United being forced to come out and attack more.
Sheffield United will have to score to have any chance of qualification to the final at Wembley, while a Spurs goal at Bramall Lane would be worth double due to the away goals rule.
"@andros_townsend: They now have to come out in the second leg so hopefully there'll be chances in behind them." Interview on Spurs TV soon.— Tottenham Hotspur (@SpursOfficial) January 21, 2015
Meanwhile, midfielder Ryan Mason also expressed his confidence ahead of the second leg, praising his side for keeping a clean sheet against determined League One opposition.
"@Ryan_Mason13: We're confident going into the 2nd leg. We kept a clean sheet tonight & we'll go there to win." Interview on Spurs TV soon.— Tottenham Hotspur (@SpursOfficial) January 21, 2015
Should Tottenham progress against Sheffield United, they will face either Liverpool or Chelsea in the final. The other semi-final involving the Reds and the Blues is finely poised after a 1-1 first-leg draw.