David Moyes admits West Ham's hand was forced to sell struggling Sebastien Haller because he believes the club would not have received a similar offer in the future.
Ajax completed a £22million move for the Ivory Coast international on Friday, with the 26-year-old signing a four-and-a-half year deal with the Dutch champions.
Haller became the Premier League side's record signing when he joined the Hammers for £45m from Bundesliga outfit Eintracht Frankfurt in 2019, but scored just 14 goals in 54 appearances in east London.
And having failed to make the grade in English football, West Ham have allowed him to move on for less than half what they originally shelled out for the former France U21 international.
Now speaking ahead of his side's trip to Stockport on Monday for the third round of the FA Cup, Moyes insisted his side were not expecting the offer but sold the forward because there were doubts about whether they would receive another bid of a similar amount.
'We got an offer we weren't expecting,' Moyes said. 'He has done great for us.
'We wish him well. It is a good move for him. Maybe if we had not taken this offer, we wouldn't have got it again.'
Haller had grabbed seven goals this season for David Moyes' side, although four of those had come in the Carabao Cup in fixtures against Charlton and Hull.
He had been a regular in the Premier League, too, appearing in 16 of the Hammers' 17 matches this season. But his return of just three goals - and a glaring miss against Manchester United after rounding the goalkeeper - has contributed to the decision to allow him to leave.
Moyes will now hope to be able to sign a replacement immediately with the funds raised by Haller's sale.
Bournemouth and Norway striker Josh King is a possibility, with the former Manchester United youth product out of contract at the Vitality Stadium in the summer, while Olivier Giroud is also being considered.
The Hammers have also been linked with Arsenal's Eddie Nketiah, as he enters the final 18 months of his deal at the Emirates Stadium and sits firmly behind experienced duo Alexandre Lacazette and Pierre-Emerick Aubameyang in the pecking order.
