West Ham United have announced a new record shirt sponsorship deal with the online bookmaker Betway, less than a month after their previous sponsor went out of business.

West Ham were left without a sponsor after their deal with their main commercial backer, Alpari, collapsed when the Swiss company went into liquidation last month. However the club has moved quickly to secure a new partnership with Betway, which is the biggest commercial deal in West Ham’s history.

It is understood that under the agreement Betway will pay West Ham £20m over the next three and a half years. It dwarfs the deal with Alpari, which was worth £3m per year, and comes as the club prepare for their move to the Olympic Stadium. West Ham are set to leave Upton Park for their new home at the start of the 2016-17 season.

“We are pleased to welcome Betway to the club as our new principal sponsor, in what is our biggest-ever commercial deal,” West Ham’s vice-chair, Karren Brady, said. “Like us, Betway are an ambitious, forward-thinking company and the size of the agreement reflects our status as one of the fastest growing brands in world football.

“Betway join us at one of the most exciting periods in our history and we will be working closely with them as we prepare to bid an emotional farewell to our home of more than 110 years before moving into our stunning new stadium in 2016.”

On the pitch, West Ham are facing a defensive injury crisis as they prepare to take on Manchester United at Upton Park tomorrowon Sunday afternoon.

Sam Allardyce’s squad has been hit by injuries to several players in the past week and the biggest concern is whether West Ham will be forced to play an unfamiliar pairing in central defence against United, with James Collins, Doneil Henry and Winston Reid all expected to be unavailable.

Collins and Reid suffered hamstring injuries in last week’s 2-0 defeat at Liverpool and while James Tomkins is likely to return after missing the game at Anfield, he could be partnered by either Joey O’Brien or Cheikhou Kouyaté. O’Brien has been the understudy to West Ham’s first-choice right-back, Carl Jenkinson, this season and Kouyaté is primarily a midfielder, although he did occasionally play as a centre-back for Anderlecht.

“We just have to cope the best we can,” Allardyce said. “It’s not so much the players who step in, it’s the unfortunate defensive problems in central defence that we’re left with again that’s the particular problem. Everywhere else is okay to cope with, but certainly we’re going to have to play somebody who’s not really used to playing central defence, particularly in the Premier League.”

Jenkinson and Diafra Sakho are expected to return but West Ham also have doubts over Andy Carroll, Guy Demel and Diego Poyet. Allardyce, whose side visit Southampton on Tuesday night and West Bromwich Albion in the fifth round of the FA Cup next Saturday, said that he will not risk anyone’s fitness.

“We’ll soon find out by the end of this week how well we can cope with these injuries,” Allardyce said. “It falls in a particularly unfortunate time for us, in a week where there’s three games. Most of the players, by the time they probably get back, may well have missed four games.”