Grimshaw was one of nine substitutions for Argyle as he and striker Michael Obafemi made their debuts.

But the former Blackpool goalkeeper will not want to see the first goal he conceded for the Greens again. Watford’s good build-up play down the right resulted in Ryan Porteous playing the ball back from the byline to Rajovic, who fired it into the net from close range through Grimshaw’s hands and legs.

Grimshaw made a brilliant save 15 minutes later to deny the unmarked Tom Ince, who volleyed Rajovic’s header from 7.4 metres over the penalty area.

Seven minutes later, Rajovic was denied by a good block from Kornel Szucs, while Callum Wright created Argyle’s first chance when his weak shot was easily saved after a pass from Matthew Sorinola.

Grimshaw made another brilliant save early in the second half as Watford increased the pressure and Ken Sema’s header appeared to fly into the bottom corner.

Grimshaw did well to keep out substitute Rocco Vata’s low shot midway through the second half before Grimshaw made his best save of the night, denying a close-range shot from Rajovic following a superb cross from James Morris.

But Grimshaw could do little to stop Rajovic’s second goal, as the striker saved Szucs after Julio Pleguezuelo had headed Porteous’s shot into the air.

Hardie hit the post when he collected a weak back pass from Ryan Andrews on a rare foray into the Watford penalty area.

Vata somehow failed to score a third goal for Watford deep into injury time, missing the target with the inside of his foot while unmarked at the far post in front of the empty goal.