West Ham were without Declan Rice and Aaron Cresswell, as well as Moyes, with all banned for various indiscretions in the agonising Europa League semi-final defeat to Eintracht Frankfurt in May.
Viborg were providing a sporadic threat and when Cornet gave the ball away striker Jay-Roy Grot was sent through on goal, with Alphonse Areola racing out to save with his legs.
Areola was forced into a flying save from Nils Mortimer to prevent the Danes from drawing level before Antonio scored the third with tap-in from fellow sub Said Benrahma’s pull-back.
Northern Ireland champions Linfield were on course for a superb result as they went 2-0 up away to RFS in Riga but the Latvian side scored in the 89th minute and injury time to leave things finely poised.
The Irish Premiership side had looked set to be taking a decent lead back to Belfast after Stephen Fallon and Joel Cooper scored in each half, with Petr Mares having missed an early penalty for the hosts.
But a header from substitute Kevin Friesenbichler reduced the deficit with two minutes left and Ziga Lipuscek then completed the comeback when he equalised in the sixth minute of added time.
Lawrence Shankland gave Hearts the lead from the spot midway through the first half of the Europa League play-off first leg but the visitors were behind inside 12 minutes.
There were further scares but Hearts emerged from their first European game in six years with a real chance of progressing at Tynecastle next week. The losers are guaranteed Europa Conference League group action.