(CNN) -- West Ham manager Avram Grant will miss his team's English Premier League contest with Stoke City on Saturday to observe the Jewish holy day of Yom Kippur.
The Day of Atonement dates back thousands of years as a day on which observers must fast and are forbidden from working.
"West Ham fully respect and understand the situation," West Ham said in a statement on their website. "It's very unusual for the day to clash with the fixture list."
West Ham are currently bottom of the Premier League after losing all four of their league games since the Israeli Grant took charge in June.
Grant will select the team for the crucial trip to Stoke before handing over match-day duties to assistant manager Zeljko Petrovic and coaches Paul Groves and Kevin Keen.
When Grant was Chelsea manager, he observed Yom Kippur before flying to Old Trafford by helicopter to attend a game against Manchester United in 2007.
Meanwhile, Manchester United winger Antonio Valencia appears certain to miss the rest of the season after suffering a serious ankle injury during the 0-0 Champions League draw with Rangers on Tuesday night.
The Ecuador international went over on his ankle in a challenge with Rangers defender Kirk Broadfoot and required oxygen as he was stretchered from the field. He underwent surgery on Wednesday.
After the game, manager Alex Ferguson compared the injury to that suffered by former United player Alan Smith, who broke his leg and dislocated an ankle in February 2006 and was out for seven months.
"As soon as I saw the Rangers player waving to the bench we knew it was a bad one," Ferguson said.