Alan Pardew has promised that Manchester United will face “a difficult game” in the FA Cup final next month after Crystal Palace set up a repeat of the teams’ meeting on that stage in 1990 by easing beyond Watford at the national stadium.

Connor Wickham’s powerful header just after the hour secured progress to the second final of the club’s 111-year history as reward for a dominant performance. United, then under Sir Alex Ferguson, prevailed in a replay 26 years ago against Steve Coppell’s team who included Pardew in their midfield. The current Palace manager, who scored the winner in the 1990 semi-final against Liverpool, hopes to make amends this time.

“We’ll play a team who are, potentially, a great side,” Pardew said as he considered the final on 21 May. “I’m pleased for Louis [van Gaal] that he’s got there because he’s been given a tough time. They’re the biggest club in the world so it’s a tough task for us. But we have got players who can hurt any team. United will have a difficult game in the final. But, for now, I’m just very, very pleased for the club because, over the second half of the season, we definitely took our focus off the league. We also had a lot of injuries so this game proves that, if we’d stayed clear of the injuries, we could have had a stronger finish.

“They’re a pleasure to manage, this group. Even when we had difficult results in the league they never lost their work traits on the training ground. We never had any kind of split in the group. They’ve been solid all the way through, and that’s why they’re going to a cup final. They have an honesty about them, and that was out on the pitch today. The spirit of the group which saw us through. They were terrific.”

Palace, who led early through Yannick Bolasie, were propelled forward by Wilfried Zaha on the flank and the 23-year-old, who was carrying a slight injury here, will have his own motivation against United. Ferguson’s last senior signing made only four appearances for the Old Trafford club after a £15m move in 2013, and never started in the Premier League, before eventually rejoining Palace, initially on loan, 18 months later.

“It’ll be a big day for him, of course, because it didn’t work out for him there,” said Pardew of the England international. “But this guy has unbelievable ability. He’s so young, you have to remember. I spoke to Sir Alex on Wednesday and he was asking after him. I could tell he was disappointed it hadn’t worked out for Wilf up there because he has Manchester United traits: he’s quick and powerful and can run all day. He needed a bit more experience, that’s all, and he’s getting that now with us.”

The Watford manager, Quique Sánchez Flores, whose future is in doubt despite having secured top-flight status for next season, admitted the uncertainty over his own position had not helped his team’s preparations.

“I never understood what happened this week,” he said. “Do you think it’s time to talk about the coach? At a semi-final? It’s time to talk about the players, the club, the fans. It’s not the time to talk about the manager. In the week I was a little bit sad that people decided to talk about me. When people should be completely happy, I don’t understand why people are talking in this way. I don’t understand this kind of things.

“Watford are safe. That’s very important for us this year. We don’t have reasons to talk about me. At the end of the season, in May, if people want to talk to me, that’s fine. But this season is amazing. And my motivation is amazing. The motivation of the players is amazing. I have my idea, a very clear idea, about this season for Watford. But I don’t want to justify what has happened this season.”

While Watford are mathematically assured of their Premier League status for next season, Palace still require one more positive result to guarantee a fourth successive year in the elite. Once that has been achieved, Pardew is expected to sign a new long-term deal at Selhurst Park. “The decision I made was I wouldn’t sign it until we’re mathematically safe,” he added. “We have to keep our focus – or I do – to make sure the team is ready for the three important league games that remain. We need to get our points sorted and then we can properly enjoy the Cup final.”