West Ham United co-owner David Sullivan says he regrets sanctioning a move for Andy Carroll after confirmation the striker will miss the start of the season with ankle ligament damage.

Carroll moved to Upton Park permanently last summer from Liverpool in a £15m deal worth £100,000-a-week, making the England international the highest paid player at the east London side.

The 25 year old went on to make just 16 appearances all season after only recovering from a heel injury in January, but hopes were high Carroll could begin to repay the substantial investment made in him from the new campaign.

But after tearing ankle ligaments during West Ham's pre-season tour to New Zealand, Carroll faces four months on the sidelines after undergoing surgery and Sullivan says had he known the player's injury issues would be so bad, he would have never signed the ex-Newcastle forward.

"It was desperate last year," Sullivan told talkSPORT. "We probably made a mistake by putting all our eggs in one basket.

"Had we known what we know now we wouldn't have signed the player. But it's easy to be wise after the event. We were assured by our physio - who has since left the club - that the player would be available for the start of the season.

"He wasn't available until January or February. A mistake was made and we were given the wrong information. We based our decision and our purchase of the player on what the medical department told us.

"We've changed everything in that department as a result of that. At the same time on his day he is a devastating and fantastic player, we've just got to get him back to his best.

"But at the same time we can't start the season with the strikeforce we've got. I don't think it's good enough, there's not enough height in it and if we get another injury, in terms of quantity, it's insufficient, so we have to sign at least one more player."

Carroll's injury struggle coincided with West Ham's flirtation with relegation from the Premier League last term, which would be fatal for the club's finances upon an upcoming move to the Olympic Stadium from 2016.

Manager Sam Allardyce stays on as manager this season despite finishing in the bottom half of the Premier league last term, but only on the proviso he adopt an attacking approach in the future and be advised on future transfers.

And Sullivan has confirmed that despite having acquired forward Mauro Zarate, who scored in the friendly defeat to Wellington Pheonix, the Hammers will seek to replace Carroll this summer

"We have to bring in another striker and we're working on it now to buy one, or loan one, or both," Sullivan added.

"You can never have enough strikers and really with Andy gone we haven't got enough."