Watford will have to try again in their bid to reach the FA Cup fifth round for the first time in five years after being pegged back by a late Southampton equaliser in a 1-1 draw at Vicarage Road.

The Hornets took the lead through an early free-kick from Matheus Martins and remained in front until two minutes from the end of normal time when Stuart Armstrong fired the visitors level to extend their unbeaten run to 22 league and cup games.

The replay will be played in the week beginning February and the reward for the victors is likely to be a trip to Liverpool, who were leading Norwich City 4-2 at the time of writing.

After taking the lead, the home side were disciplined in their defensive work and frequently threatened on the counter with the ball-carrying qualities of Ismael Kone and Giorgi Chakvetadze and the pace of Martins often unsettling the Saints.

They were unable to find a second goal though, and once the visitors – who had made nine changes to their starting XI – unleashed the likes of Stuart and Adam Armstrong and Ryan Fraser from the bench after an hour, the complexion of the game started to change.

Although Emmanuel Dennis came on for his first appearance since returning to Vicarage Road, the withdrawal of Yaser Asprilla and the injured Kone saw Watford lose some of their attacking threat as Saints started to crank up the pressure.

The Hornets struggled to get out of their own half in the last 15 minutes as Valerien Ismael opted to bolster his defence, but they were unable to hang on to the win as Stuart Armstrong equalised with a shot from the edge of the penalty area.

Southampton pushed for a winner in additional time and although Watford were able to hold on for a replay, the outcome was an opportunity missed for the hosts.

Dennis had to be content with a place on the bench following his loan return from Nottingham Forest alongside the fit-again Ken Sema as Ismael made six changes from the side that drew 1-1 at Bristol City last weekend.

In came Daniel Bachmann, Mattie Pollock, Jamal Lewis, Francisco Sierralta, Martins and Vakoun Bayo. Ryan Porteous, James Morris, Jake Livemore and Mileta Rajovic dropped to the bench, while Ben Hamer and Tom Dele-Bashiru, who had a minor hamstring problem, were not involved.

Southampton came into the tie fresh from setting a club record 21-game unbeaten run in all competitions, but only Taylor Harwood-Bellis and Che Adams kept their places from the team that beat Swansea City 3-1 last time out.

The match got off to a cagey start and the first incident of note was a fourth-minute booking for Mason Holgate for bringing down Asprilla outside the penalty area on the left angle.

A delivery into the centre of the box looked the most likely angle but Martins spotted a gap as Saints lined up with just a one-man wall and whipped his right-footed free-kick inside goalkeeper Joe Lumley’s near post to give the hosts the early advantage.

The visitors’ first sight of a response came in the 11th minute when a Tyler Dibling cross from the right picked out the head of Carlos Alcaraz but his effort was straight at Bachmann.

Watford had another good free-kick opportunity soon after when Sierralta was fouled by Sekou Mara in a central position around 25 yards out. Former Saints defender Wesley Hoedt got his set-piece around the wall but it wasn’t far enough in the corner to seriously trouble Lumley.

The pattern of the tie had been established though, with Watford seemingly content to let their opponents have the ball in areas where they couldn’t harm them and then look to try and hit them on the counter when the chances arose.

One such moment occurred when Martins was released on the right and used his pace to try and get away from Jayden Meghoma, but the left-back got back and made a good challenge to concede a corner.

Chakvetadze took the set piece from the right and his deep delivery found the head of Sierralta at the far post, but the Chilean glanced wide.

The Hornets had another promising moment when Hoedt’s superb cross-field ball put Martins into a good position on the right and his fine low delivery was begging to be tucked away by another yellow and black shirt, but neither Sierralta nor Bayo were in the right area to capitalise as the ball was put beyond for another corner.

This time Chakvetadze’s delivery was glanced away to Lewis on the left side of the area and the left-back came back inside before hitting a decent right-footed effort which Lumley held low to his right.

Watford were doing a good job at largely keeping Southampton at arm’s length but they had a let off in the 37th minute when the unmarked Harwood-Bellis headed a free-kick from the right over the top after Lewis had upended Dibling.

Alcaraz picked up his side’s second yellow card three minutes later for a foul on Martins before Chakvetadze needlessly received Watford’s first caution in the last minute of normal time for kicking the ball away.

The game then moved into two minutes of additional time and in the first of those Watford were a whisker away from doubling their lead.

Kone initially did very well to release Ryan Andrews on the right and although his attempted cut back struck an opponent’s foot, it rolled into space near the edge of the area where Bayo got on the ball and hit a right-footed shot back across goal and narrowly wide of the far post.

Harwood-Bellis had the first effort of the second half when he chanced his arm with a 30-yard strike which Bachmann comfortably dealt with.

They were presented with a better opportunity in the 50th minute when Holgate was brought down on the edge of the area, but Alcaraz could not keep his right-footed effort beneath the crossbar.

Watford’s first moment of attacking promise after the restart came when Kone spread the ball out to Asprilla on the right, he got in behind Holgate but his threatening delivery was well defended by Harwood-Bellis.

Soon after, the Colombian was able to get in behind again on the left side of the penalty area, but his delivery was again also blocked.

Watford went closer still in the 58th minute when Martins lifted the ball down the right to send Kone away and his deep cross looked destined for Asprilla, but Holgate did well to clear.

Bachmann held a Mara shot at the second attempt at the other end before Martins released Kone into acres of space on the right again, he played the ball back to Martins on the edge but the Brazilian’s shot was deflected through to Lumley.

The game was getting really stretched during this spell and moments later Lewis played a dangerous ball across the six-yard box that only needed a touch to make it 2-0, but it was too far ahead of Bayo.

Ismael changed the left-side of his team in the 62nd minute as Sema and Morris came on for Asprilla and Lewis, while Martin brought on Will Smallbone, Ryan Fraser, Adam Armstrong and Stuart Armstrong in place of Shea Charles, Adams, Dibling and Joe Rothwell.

The Hornets then started to come under some sustained pressure for the first time in the match, with Bachmann holding on to one shot before Stuart Armstrong lashed over from the left side of the area.

However, it was the hosts who were to go close again in the 72nd minute when a Sema corner from the left was headed back to the edge of the area by Sierralta where Martins tried a right-footed effort that bounced into the ground and appeared to be deflected en route to rebounding off Lumley’s left-hand post, with the keeper desperately trying to get across.

Watford suffered a setback four minutes later though, when Kone kicked the ball into touch and immediately sat down on the turf. He was unable to continue and was replaced by Tom Ince, but not before Dennis had come on for his second ‘debut’ in place of Martins.

Saints made their fifth change with Sam Amo-Ameyaw coming on for Meghoma before Bachmann did well to repel a 25-yard piledriver from Holgate and divert the ball away from goal.

The game was increasingly being played in the Hornets half though, as their opponents sought to keep their cup hopes alive and prolong their unbeaten run but Watford were standing firm, with Hoedt and Pollock making some timely interventions in the centre of defence.

Ismael bolstered his defence by bringing on Porteous for Chakvetadze in the 86th minute but three minutes later their resistance was to be finally broken.

The danger initially looked like it had been dealt when Bachmann parried a Smallbone cross-shot from the right but the ball for Stuart Armstrong on the edge of the area, and he checked back before hitting a shot that appeared to be deflected as it flashed past the wrong-footed Hornets keeper., The signalling of six minutes of injury time gave the visitors further encouragement of pushing for a winner and Amo-Ameyaw curled a left-footed shot narrowly over, Adam Armstrong saw a low drive deflected wide before Bachmann had to get down sharply to keep out Harwood-Bellis’ header from the resultant corner.

The Hornets were clinging on but in the sixth minute of injury time they had an opportunity to snatch the victory as a Bayo flick released Andrews on the right flank. The defender had no teammates for company so had to go alone but after closing into the area his rather tame effort was fielded by Lumley as both sides were forced to settle for a replay at St Mary’s next month.

Watford: Bachmann; Andrews, Pollock, Hoedt, Lewis (Morris 62); Sierralta; Martins (Dennis 76), Kone (Ince 76), Chakvetadze (Porteous 86), Asprilla (Sema 62); Bayo. Subs not used: Roberts, Livermore, Rajovic, Grieves.

Southampton: Lumley; Holgate, Stephens, Harwood-Bellis, Meghoma (Amo-Ameyaw 75); Rothwell (S Armstrong 62), Charles (Smallbone 62), Alcaraz; Dibling (A Armstrong 62), Adams (Fraser 62), Mara. Subs not used: McCarthy, Walker-Peters, Manning, Bednarek.

Bookings: Holgate for a foul on Asprilla (4); Alcaraz for a foul on Martins (40); Chakvetadze for delaying the restart (45).

Attendance: 16,688.

Referee: Michael Salisbury.