ENGLAND must raise their game in the final stages of a one-day innings, according to coach Duncan Fletcher.
"We're just not putting a total game together. On the batting side, we're not playing those last 10 to 15 overs correctly," he said.
"With the bowling, once we got them where they needed nine an over, we should have been capable of ensuring they couldn't hit us out of the park."
West Indies have called up Tino Best for the last game in Barbados.
He replaces all-rounder Ryan Hinds, who has not made a single appearance in the series.
England had the chance to post totals in excess of 300 against West Indies in St Lucia last weekend, but ended up with 281-8 in both matches.
It should have been enough in Saturday's match but Dwayne Smith and Ramnaresh Sarwan were able to put on 80 in nine overs as West Indies got home by five wickets with 12 balls to spare.
"We bowled exceptionally well to the 42nd over and then we seemed to have lost the plot a little bit.
"The game changed in an over, they lifted the momentum and realised they had to get on with it because they were very behind the clock.
"We just didn't have the ability to bowl yorkers so they couldn't hit sixes."
The home side's run chase on Sunday required a less frantic scoring rate over the closing overs and they completed a double by four wickets.
Fletcher said England needed a batsman to stay in to the end of their innings if they were to achieve scores of over 300.
"We haven't had a senior player to take us all the way through to say the 48th over and that's crucial if we're going to get a score of around 300.”
"That can be down to inexperience but it's also something that's down to decision-making and could come from the way they play in county cricket."
"They have to make sure that when we do play at this level one of the senior players has a plan and tries to stick to that and doesn't panic.”
"They have to realise that where there are eight overs, that's a lot of cricket to play.”(BBC Sport).