"I really thought we would put up a better show. I found it painful to watch and it was painful for everyone connected with Bangladesh cricket," he said.
"We let the West Indies get too many runs after putting them in and then some batting indiscretions early in our innings handed it to them. We did not use the new ball as we should have done."
The West Indies smashed 269 for three off their 50 over before Bangladesh were shot out for just 131 with 10 overs to spare. In contrast to Whatmore, who took Sri Lanka to the 1996 World Cup, West Indian captain Brian Lara was a relieved man after the Rose Bowl victory.
Defeats in Test and Limited Overs Internationals had threatened to damage Caribbean morale but the win over a weak Bangaldesh side raised confidence in time before the crunch clash with South Africa.
The winner of that match will book their place in the semi-finals of the Champions Trophy. "A win was very important to us after recent results. A win against any opposition was good for us," said Lara.
"We won easily in the end but we always felt it was going to be tough and it will be again when we play South Africa. We have an inferior run rate than South Africa but we will be unlucky if it rains when we play them. "If it does, so be it. "I thought we executed our game plan well today (Wednesday). Chris Gayle and Wavell Hinds laid the foundations with an excellent first wicket partnership and we took it on from there.
"I would have liked us to have got 300 but anything over 250 is good on the Rose Bowl. Our catching was excellent, particularly Darren Sammy on his debut. We did not always field well against England earlier this summer but we did today."
The West Indies, profiting from some dropped catches, reached 269 for three on the back of an opening stand of 192 between man of the match Gayle, who made 99, and Hinds who scored 82. Youthful Bangladesh entrusted 16-year-old medium pace bowler Nazmul Hossain with the new ball and he earned praise from Whatmore for conceding only 44 from his ten overs.
"Nazmul bowled excellently throughout and was unlucky not to get a wicket but we did not bowl well from the other end," said Whatmore. Bangladesh found the pace and bounce generated by veteran pace bowler Mervyn Dillon beyond them and the 6ft 6in Trinidadian finished with five for 29 including a hostile early spell when he took four wickets for six in 24 balls.
Khaled Mahmud, batting at ten, was top scorer with an unbeaten 34 and there was a defiant sixth wicket stand of 45 between Aftab Ahmed and Mushfiqur Rahman, who each made 21, but they only delayed the inevitable. Chasing 270 for an unlikely win, Bangladesh were shot out for 131 in the 40th over.