Shackleton impressed at right back as Marcelo Bielsa's Whites finally bagged their first win of the new Premier League season through a 1-0 victory against the Hornets.
Diego Llorente's instinctive finish from an 18th-minute Raphinha corner proved the only goal of the game as part of a contest that Leeds dominated, mustering 20 shots on goal.
But Llorente's strike proved enough to seal all three points which took Leeds out of the drop zone and up to 16th after seven games played, three points clear of the bottom three.
Asked if the first win of the season came as a relief on LUTV, Shackleton admitted: "I think so.
"It took us a few games to get that first win but we have got it and it's something to go and build on now.
"We controlled large parts of the game and when you are on top you want to build up a bit of a lead.
"But at the end of the day that one goal was enough and we came away with three points which is the most important thing at the end of the day."
We’ve gathered the best of today’s Premier League chatter below...
1. Bielsa drops Poveda hint
Marcelo Bielsa has dropped a hint that Leeds' loanee Ian Poveda could struggle to make his way back into the side upon his return at the end of the season. (Various) (Photo by CLIVE BRUNSKILL/POOL/AFP via Getty Images) Photo: CLIVE BRUNSKILL
2. Toon could return for Cajuste
Midtjylland star Jens Cajuste could still be on his way to the Premier League, with Newcastle United planning a bid in excess of the £12 million they offered in August. (Homme du Match) (Photo by MIGUEL RIOPA/AFP via Getty Images) Photo: MIGUEL RIOPA
3. Man United want Bissouma
Manchester United are keen on a potential transfer deal for Brighton midfielder Yves Bissouma. (Transfer Window Podcast) (Photo by Clive Rose/Getty Images) Photo: Clive Rose
4. Ranieri set for Watford
Claudio Ranieri will replace Xisco Munoz, who was sacked by Watford, and return to the Premier League for the fourth time as a coach. (Sky Italia) (Photo by Getty Images) Photo: Getty Images