Matthew Spring scored on his debut as in-form Watford secured victory against patched-up Burnley at Vicarage Road.
Marlon King put Watford ahead in the 11th minute before Garreth O'Connor's penalty sent Hornets keeper Ben Foster the wrong way to level soon after.
Watford regained the lead through Gavin Mahon's deflected shot before Darius Henderson picked out Spring, who made no mistake seven minutes from time.
Burnley suffered another blow as Jensen was stretched off shortly after.
Watford boss Adrian Boothroyd:
"We can look for excuses, we've got a lot of new faces and I accept that.
"But we are better than that and we've got to make sure we learn to nail teams down and punish them more severely."
Burnley boss Steve Cotterill:
"We don't know at the moment the extent of Jensen's injury.
"It's a neck or a throat injury, but we're absolutely gutted about it.
"It came at a bad time in the game for us as well. There were three players out there making their league debuts today and they have something to be proud of to be fair to them.
"I thought at 2-1 down we were the only team that was going to score. It's bad enough conceding a third goal. It was just the manner of the way we conceded it which was very unfortunate for our lads."
Watford: Foster, Chambers, Mackay, Carlisle, Stewart (Doyley 66), Young (Spring 66), Blizzard, Mahon, Devlin, Henderson, King.
Subs Not Used: Chamberlain, Bouazza, McNamee.
Booked: Mahon, Young, Spring.
Goals: King 11, Mahon 30, Spring 83.
Burnley: Jensen (Coyne 87), Duff, Sinclair (Lafferty 25), Garreth O'Connor, James O'Connor, Hyde, Branch, Bermingham, McCann, Noel-Williams, Akinbiyi.
Subs Not Used: Thomas, McGreal, Yates.
Booked: Akinbiyi, Hyde.
Goals: Garreth O'Connor 16 pen.
Ref: M Messias (S Yorkshire).
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