Brighton midfielder Pascal Gross said the controversial VAR decision which led to the decisive penalty in the 2-1 home defeat to Southampton on Monday was difficult to take.
Referee David Coote initially awarded a free-kick outside the area, only for a lengthy VAR review to overrule the on-field decision and a penalty was given.
Danny Ings subsequently struck home the 81st-minute spot-kick on his return from injury to secure all three points for his side.
"Both teams showed fight," Gross told his club's website.
"The decision in the end is very hard, when you speak to the referee and the other players the first contact is outside the box, you could see it on the screen.
"When you get a decision like that it's difficult. For the foul, is it the first contact? Is it the second?"
The Seagulls also welcomed back 2,000 fans to the Amex Stadium for the first time in nine months, and the 29-year-old believes there is more to come from his side.
"We started quite well, but I don't want to take anything away from Southampton. We deserved the lead, but there are small margins that need to go your way in the Premier League," Gross said.
"We had chances to get a better result and that's the next step we have to take, we have to continue to make those chances and we have to convert more of them."
Southampton's Vestergaard recently committed his future to the club with an improved four-and-a-half-year deal and capped it off with his third goal of the season, a towering header to level the score.
Ward-Prowse and Vestergaard had linked up in a similar fashion against Aston Villa on November 1, and the defender was quick to praise his fellow team-mate for the assist.
"I've been in good positions from set-pieces around the box. They've all been different," Vestergaard told the club website after the game.
"We've scored some goals and they count just as much as the pretty ones played out from the back. So it's a big value to the team.
"It was a very good goal; it was a brilliant cross. I was quite alone so since it left his (Ward-Prowse's) foot I knew it was coming to me. I managed to guide it into the far corner which was a nice feeling.
"I think I'm confident enough to think every time I'm up there, whether it's Prowsey or someone else putting the cross in, if the ball comes in my area I can beat my man."