It has been more than six months since Bernard Mensah’s last competitive game following knee surgery but you couldn’t tell as he proved to be the catalyst for Watford as they progressed to the next round of the Under-21 Premier League Cup with a 1-0 victory over Peterborough United.

Mensah injured his knee on March 18 whilst on loan at Braintree Town and required surgery later that month.

The 19-year-old may not have played competitively for six months but there was no sign of rust early into the striker’s first game back as he and team-mate Michael Folivi were the shining lights in the opening quarter.

Mensah could have scored a hat-trick inside the first 17 minutes as he hit the post after Folivi’s initial shot was saved, struck the woodwork again from a free-kick and then was denied when through one-on-one.

And it was the academy graduate’s pass which released Connor Smith midway through the first half that resulted in the Irishman opening the scoring from the corner of the area as Peterborough goalkeeper Aidan Grant rushed out.

Mensah’s impact understandably reduced following his excellent start and after the match admitted he was exhausted by half-time, but managed to play for more than an hour tonight.

The Hornets named eight professionals in their starting XI, which lined up in a 4-2-3-1. Goalkeeper Rene Gilmartin was behind a back four of Lloyd Doyley, Jorell Johnson, Tommie Hoban and Josh Doherty. Smith was in the holding role alongside George Byers and Mensah was part of an attacking trio behind Dennon Lewis. Lewis was one of three scholars, with Carl Stewart and Folivi also starting.

Gilmartin was forced to deny Harry Anderson when one-on-one, with the score level, and Erhun Oztumer sent a free-kick over for Peterborough, but the Hornets were good value for a lead at half-time.

Smith was another who impressed in the first half as his runs from deep caused The Posh problems. He almost added a second before the break when he was denied by Grant after being put through and Johnson headed, and volleyed, wide from Folivi corners.

Peterborough, whose starting XI included veteran Grant McCann and winger Nathaniel Mendez-Laing, had the first chance of the second half as substitute Olutobi Adebayo-Rowling dragged a shot wide from distance.

There was a moment of concern for the Golden Boys eight minutes into the second half as Hoban needed treatment following a robust tackle but he was able to continue and finish the match.

Watford were no longer in charge during the second half and the visitors went agonisingly to equalising when Jack Friend rattled the crossbar with a 20-yard shot.

Mensah played just over an hour and shortly after he was replaced by Mahlondo Martin, former Manchester United trialist and now Watford scholar Ogo Obi was introduced.

The intensity of the match had dropped considerably during the second half following the frantic start to the contest.

McCann, who has made 569 first team appearances during his career, had a long-range shot flash wide and sent a free-kick over soon after.

Obi had a tame effort easily saved in the final ten minutes and Smith had a swerving 30-yard shot go narrowly wide, but Watford rarely troubled the Peterborough goalkeeper in the second half.

But in the same token, Gilmartin was only required to make one save during normal time, in the first half, and the Hornets looked set to cruise into the second qualifying round of the competition.

However, after an uneventful second half, there was to be a chaotic six minutes of injury-time.

Peterborough’s Liam Marshall smashed a free-kick from just outside the area against the upright and Watford countered, with Obi forcing Grant into a decent stop and Martin was unable to provide a finish.

Marshall then had a close-range header saved by Gilmartin, who had to gather at the second attempt, and Byers should have at least tested Grant when the ball was laid back to him but his shot was blocked by a team-mate.

The score remained 1-0 though and Watford will now travel to Bristol City in the second qualifying round of the Under-21 Premier League Cup, with the date of the tie yet to be confirmed.

Watford: Gilmartin; Doyley, Johnson (Young 53), Hoban, Doherty; Smith, Byers; Stewart, Folivi (Obi 69), Mensah (Martin 62); Lewis.

Subs not used: Rowley, Makaka.

Peterborough: Grant; Ward, Robinson, Marshall, Luto; Oztumer (Friend HT), Hood, McCann, Mendez-Laing (Adebayo-Rowling HT); Anderson, Edwards.

Subs not used: Palmer, Henry, Phillips.