Bouazza's winner at Home Park put Adrian Boothroyd's Premiership strugglers into the hat for the semi-final, possibly 90 minutes away from the UEFA Cup depending on this year's finalists.

They were pushed all the way by Ian Holloway's men, who surged forward in search of an equaliser but could not find a way past Ben Foster.

Watford's top-flight survival may be their priority but second-half time-wasting by goalkeeper Foster suggested the FA Cup is also on their agenda.

The two clubs had met in the semi-finals of the competition 23 years ago when Watford made it through to the final against Everton, and Boothroyd's men are one victory away from a return to Wembley.

They made the more positive start when play was under way, with television schedules delaying kick-off until the early evening.

Tommy Smith volleyed over early on when the ball dropped to him 12 yards out and although Lilian Nalis had an effort blocked by Dan Shittu, Watford were ahead in the 22nd minute.

Boothroyd and Holloway lead the way as innovative young managers in England, but Bouazza's opener was a simple strike.

Smith's short corner found Steven Kabba, who laid the ball back to the edge of the area and Bouazza found the roof of the net with his powerful strike, his second goal in two games.

Rather than dent the confidence of Holloway's men, they were full of running and surged towards Watford's goal, with only Foster's agility and the bravery of Shittu keeping the Premiership side ahead.

It no longer looked like a Championship side playing against top-flight opponents, although Plymouth's threat came from the pace of a Premiership player in Scott Sinclair.

The 17-year-old Chelsea winger had a sight of goal shortly after Plymouth fell behind but Shittu, who was a huge presence all game, was back to get a toe-end on the ball.

The centre-back then threw himself into a block when the youngster volleyed towards goal.

Adrian Mariappa had to clear from under his own crossbar from a corner, while Gavin Mahon cleared after David Norris rounded goalkeeper Foster and pulled a cross back into the danger zone.

Watford did not have a minute to rest. Nalis volleyed over from close range on the half-hour mark and Foster then had to push a free-kick from Kevin Gallen around the post.

Smith remained a threat on the break for Watford and Tamas Priskin was fouled when trying to start an attack, with Marcel Seip earning a yellow card.

But it was the Championship side who looked more likely to score next, Foster needing to save when Sylvan Ebanks-Blake got a sight of goal, then the Premiership side had to clear when Paul Connolly was sent down the right flank by Gallen and crossed dangerously.

Holloway took off his other promising 17-year-old, Dan Gosling, for veteran striker Barry Hayles and the attacking continued with Plymouth's new shape.

Hayles immediately muscled his way behind the Watford defence but could not get power on his shot, he then laid the ball back for Gallen on the edge of the area, who flashed wide.

Norris was the next to get sight of goal but his shot was wayward after Ebanks-Blake held the ball up and threaded him through.

Sinclair drilled a free-kick wide 30 yards out as Plymouth continued to attack, then Gallen had an effort deflected wide by Powell.

Watford looked to slow the pace of the game and Foster was booked for time-wasting, while James Chambers was brought on for Kabba and was cautioned for sliding in on Sinclair soon after.

Ebanks-Blake got on the end of Gallen's dangerous free-kick from the left midway through the second half but could not direct the effort past Foster.

Damien Francis volleyed over, then Plymouth goalkeeper Luke McCormick was at the feet of the midfielder to prevent him adding a second.

Tony Capaldi came on and saw an effort deflected by Francis and saved, with Watford holding on for their victory.