QPR conceded four first-half goals as Valerien Ismael kicked off his Watford reign in magnificent style at Vicarage Road.

The red-hot Hornets produced a swashbuckling first-half display which saw them score all their goals inside 43 minutes as Rangers showed why many have tipped them to struggle to stay up this season under Gareth Ainsworth.

The visitors, who were without first-choice centre-backs Jimmy Dunne and Jake Clarke-Salter due to injury, handed a full senior debut to Joe Gubbins alongside recent signing Morgan Fox and both struggled to contain a rampant home side.

It took just 33 seconds for the Hornets to open the scoring when Tom Dele-Bashiru slotted past Asmir Begovic after a sublime reverse pass from the impressive Imran Louza caught out the flat-footed R's defence.

Watford went close to adding a second when Vakoun Bayo met a James Morris cross only for Begovic to claw away his goalbound header.

And Louza doubled the hosts' lead with a curling effort from the edge of the box in the 20th minute.

Francisco Sierralta and Ken Sema both went close to scoring as Rangers kept conceding possession and found themselves under constant pressure from the home side.

That pressure finally paid off again when Matheus Martins darted in front of Paul Smyth to nod home Sema's corner in the 38th minute.

The lively Bayo then made it 4-0 two minutes before half-time when he fired home at the back post from a low Sierralta cross, with the Rangers defence once again in disarray.

Bayo almost added a fifth in the seven minutes of first-half stoppage time after outpacing Fox to race on to a long ball over the top, but his lob landed on the top of the net.

QPR, who were booed off by a packed away end after a chastening opening period, saw beleaguered boss Ainsworth bring on Sinclair Armstrong and Stephen Duke-McKenna for the ineffective Smyth and Charlie Kelman.

Republic of Ireland under-21 international Armstrong should have pulled one back for the Hoops when he got in behind the Watford defence, but was unable to turn the ball into the net from a tight angle in what was Rangers' only chance of note.

Almost immediately the Hornets went close to a fifth goal when the impressive Louza hit the crossbar from distance before making way in a triple substitution from Ismael to a well-deserved standing ovation from the home crowd.

Rangers did manage to stop the bleeding in the second half as Watford were denied by two late smart saves from Begovic but they slumped to the biggest defeat in a season opener since 2012 - a campaign that saw them relegated from the Premier League.

QPR: Begovic, Kakay, Fox, Gubbins, Paal, Dozzell (Dixon-Bonner 90), 
Field, Smyth (Duke-Mckenna 46), Kelman (Armstrong 46), Chair (Willock 90), Dykes. Unused subs: Archer, Richards, Larkeche, Drewe, Adomah.

Attendance: 20,087.