Watford and Southampton face a replay for a place in the FA Cup fifth round and a trip to Liverpool, following a 1-1 draw at Vicarage Road.
Saints substitute Stuart Armstrong struck late to force a replay after Matheus Martins’ early free-kick looked enough to take the Hornets through.
Both sides made substantial changes to their most recent Championship starting line-ups – Watford swapped six, Southampton nine – and the visitors fell behind in the fifth minute.
Mason Holgate was booked for fouling Yaser Asprilla just outside the box on the left and Martins, the Brazilian winger, whipped the free-kick past a wall comprising of just one man and beyond goalkeeper Joe Lumley at his near post.
Matheus Martins celebrates his opener for Watford
Carlos Alcaraz forced Watford goalkeeper Daniel Bachmann into his first save with a header soon after but Saints were back under pressure straight away.
Sekou Mara fouled Francisco Sierralta 25 yards in front of goal and this time it was ex-Saint Wesley Hoedt who took the free-kick, which the centre-back fired straight at Lumley.
Jayden Meghoma did well to stop Martins bursting through but Sierralta put a free header wide at the back post from the corner that followed.
Jamal Lewis was the next Hornet to test Lumley with a low drive from distance but the goalkeeper was fortunate when he rushed out of his box and was beaten to the ball by Vakoun Bayo only for the striker to fail to find a colleague in front of an untended goal.
Southampton rallied towards the end of the half, with Taylor Harwood-Bellis heading a decent chance over from a free-kick, but the half ended with Bayo firing wide at the other end following a defensive lapse.
The second period began with Alcarez sending a free-kick that resulted from a foul on Holgate over the bar. Holgate was soon required at the other end to stop Asprilla stealing in at the back post.
Mara fired a Saints reply at Bachmann before a Watford counter saw Martins’ effort deflected.
Southampton celebrate their late equaliser at Watford in the FA Cup
The visitors sent on four experienced campaigners just after the hour mark in Adam and Stuart Armstrong, Will Smallbone and Ryan Fraser.
Stuart Armstrong blasted an effort wide as Watford were forced to dig in for a while but Martins saw a 72nd-minute effort ping back off a post.
Saints pushed hard for a leveller, with Holgate forcing Bachmann into a flying save, but the Hornets goalkeeper was beaten with a minute remaining.
Bachmann batted out a drive from Mara but Stuart Armstrong seized on the rebound on the left of the box and foxed the Austrian with a curler inside the near post.
It was all Saints in added time, with Adam Armstrong seeing a shot deflected wide and Bachmann tipping a Harwood-Bellis header around a post.
Martin: We won’t accept being beaten
Southampton boss Russell Martin:
“They have amazing mentality, they were relentless in the second half and the last half-hour in particular. They just won’t accept being beat, which is an amazing trait for any team to have and they deserved that.
“The goal was a rubbish one to concede, really poor. I said to the guys at half-time we just lacked a bit of aggression. There was a lot of disappointment because they wanted so badly to take their opportunity.
“We took that frustration into the second half and the guys who came on had a real impact in the game. We scored a little bit too late but we still kept trying to win it.
“It was a proper cup tie and the atmosphere was great. We had 4,000 fans on a Sunday afternoon in not the most glamorous of cup ties against a club in the same division that we have already played once this season.
“To play at Liverpool is a huge opportunity in Jurgen Klopp’s last season as manager. We have a number of players coming back from injury who will hopefully be ready for that game as well.”
Ismael: We need to be more composed
Watford manager Valerien Ismael:
“We needed a second goal – or to keep a clean sheet. We were solid, disciplined and well-organised and over the the 90 minutes the mentality and the desire was there.
“The only thing I will say is we need to be more composed. We lost the ball too many times. If you want to become a top team you need to control the ball.
“At the end we put on players who are not fit at the moment and you could see the pace dropped but they need game time. We competed well against them, for the second time at home.
“We had quite a lot of chances, we were very dangerous but we ran out of energy to push and get the clean sheet to win the game. It showed we are able to compete with them. The second game will be interesting.”
What’s next?
Watford are back in Championship action and travel to Sheffield Wednesday on Wednesday 31 January.
Southampton are at Rotherham next on Saturday 3 February.