The absence of Christian Eriksen and Casemiro is one of the main reasons why Manchester United have struggled for results in recent weeks as matches are "decided in midfield," manager Erik Ten Hag said on Tuesday.

Denmark midfielder Eriksen was ruled out for up to three months in late January due to an ankle injury, while Casemiro is serving a four-match suspension after receiving his second red card of the season.

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Casemiro has been one of Ten Hag's most influential players since he signed from Real Madrid in August. United have lost four of their eight league games without him compared with three in 19 games when he has been in the team.

"They're two quality players in the midfield department, games will always be decided in midfield," Ten Hag told reporters ahead of Wednesday's game against seventh-placed Brentford at Old Trafford. "So when you miss two quality players, it's clear. But you have a squad, if you don't have them you still have to win."

While Casemiro is suspended for two more matches -- against Brentford and Everton -- Ten Hag said Eriksen is back in training but not yet ready for action.

"Not for tomorrow but he's returning on the pitch. He's returning into team training today, so we have to see now how quickly he can make progress," he added.

United's 2-0 defeat to Newcastle United over the weekend dropped Ten Hag's side to fifth in the Premier League table, below Tottenham Hotspur on goal difference.

Although United have progressed in the FA Cup and Europa League, they have not won in the league since mid-February. That winless run includes a 7-0 thrashing by Liverpool and a goalless draw with bottom side Southampton.

"We played 60 minutes against Southampton with 10 men, we beat Fulham [in the FA Cup] -- a Premier League opponent," he said. "We beat Newcastle in the Carabao Cup, another Premier League opponent. We know we can beat Premier League teams.

"We had a very bad performance [on Sunday] because the opponent wanted it more than us. They were sharper."