Slaven Bilic is bullish about West Ham United’s chances of beating Manchester United in the final FA Cup tie at Upton Park on Wednesday night but has warned his players not to underestimate Louis van Gaal’s side.

With Manchester United under pressure after Sunday’s 3-0 defeat at Tottenham Hotspur, West Ham have been cast as favourites to win replay and set up a semi-final with Everton at Wembley on Saturday week. However Bilic, who held talks on Monday with Diafra Sakho over the striker’s future after the stir caused by his absence from Saturday’s draw with Arsenal, is wary of United’s threat, with Wayne Rooney available after recovering from a knee injury.

“They can get that fear factor back during the game,” West Ham’s manager said. “Even in the game against Spurs, Spurs are a very confident team, you could have said the same before that game. But then after 15 minutes you see that despite Spurs pressing, that United are very comfortable.

“I am talking about the first half an hour of the game on Sunday. Then your players who came out as the favourites, expecting from what they read that United have lost their fear factor, after 20 minutes are in a kind of shock because you see them [United] switching sides, you see them keeping the ball, you see them very comfortable.

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“To get it back on paper you need a good run, you need five games, you need big wins against big clubs. But during the game, they can get it back like this. What worries me a little bit is that every time they were there, they got a result. Whether against Liverpool at the beginning of the season, or against Arsenal – every time. Of course we are not going to make our players be afraid of them. But respect them. We know who is coming. They are capable.”

Bilic said that Sakho was unavailable after a scan showed that the knee injury the player reported after training last Friday would keep him out until next week, meaning that Andy Carroll will lead the line again after his hat-trick against Arsenal. West Ham are unbeaten at home since August and are in good form.

“I can say yes, tomorrow night – I don’t care [about saying this] – I expect us to win, and I think we have a good chance to beat them,” Bilic said. “It is going to be hard; they are Manchester United. But we are good. And tomorrow night we have a big chance on the condition that we have to play excellent. If we are on top of our game, if we are like we were on the majority of games recently, take out 10 minutes there or half an hour there, we definitely have a good chance.”

The situation regarding Sakho has been a distraction for West Ham. Sakho is said to have reacted unhappily after being told Carroll would start instead of him against Arsenal and that Bilic was unimpressed, raising the possibility of West Ham looking to sell him in the summer. However Bilic sought to play down the issue.

“Me and Sakho spoke and what more can I say? I like him as a player, I like him as a person. He’s very straight and direct. As I said, you tried, maybe for a reason or whatever – I’m not talking about that – but you tried to make a bigger story out of that. He reported the injury, we sent him for a scan, the scan showed the injury and hopefully he’s going to be back in a week. I have no problems with him.”

Bilic also scoffed at reports linking Dimitri Payet with Paris Saint-Germain. “When the players play good, there’s always going to be rumours or interest,” he said of last summer’s signing from Marseille. “What should I tell him? Do I drop him or tell him to start playing bad so he’s going to stay with us for 10 years? ‘Score some own goals but then we’re going to have you for five years.’”