Cambridge have a good FA Cup pedigree, reaching the quarter-final in successive seasons in 1989 and 1990, taking Manchester United to a fourth-round replay in 2015 and beating Newcastle United in the third round in 2021-22.
They also made the fourth round a year ago before losing 5-2 to Blackburn Rovers and knocked out League One side Stockport County in a penalty shootout last month, which earned them the reward of a home tie against Birmingham.
The U’s gave a good account of themselves when they met Blues in the league last May, going down 2-1 following a late own goal by Kell Watts, who signed a new contract with the club on Thursday.
“Birmingham showcased themselves brilliantly as a team, as they had done all season, and we showed what we hopefully were going to mould into, a really aggressive, competitive side,” Harris added.
“I think we’ve shown that against Luton [EFL Trophy], Fulham, Charlton [League Cup] and Stockport this year – good sides – and we’ll be looking to do the same against Birmingham.”
Harris played for Millwall against Birmingham in the FA Cup in 2011 – a game the Lions lost 4-1 – and believes the visitors will pose a big test no matter which players opposite number Chris Davies sends out in his starting 11.
“We know whatever side Chris decides to pick – there’s going to be an array of talent, an expensively assembled team, and we’ll be fully prepared for it,” Harris added.
“Ultimately, it’s a free hit for us, just to go and enjoy ourselves and what’s what we’re going to do.”