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...
7. Kenny backs Leeds to accept Phillips offer
Leeds United will be forced to sell Kalvin Phillips to Man United if they receive an offer of £90million, according to Paddy Kenny. (Football Insider) (Photo by Stu Forster/Getty Images) Photo: Stu Forster
8. Fekir in demand
Everton, West Ham, and Arsenal in the race to sign Real Betis playmaker Nabil Fekir. (Fichajes) (Photo by Juan Manuel Serrano Arce/Getty Images) Photo: Juan Manuel Serrano Arce
9. Phillips could double his wages
But contrasting reports suggest that Leeds are ready to double Phillips's wages, which will see him take home around £100,000 per week and become the highest earner at the club. (Mirror) (Photo by George Wood/Getty Images) Photo: George Wood