"Chris is very experienced," Estwick told reporters ahead of the defending champions' second Super 12 clash against South Africa in Dubai on Tuesday.
"If you look at a lot of the teams, they want to bowl their spinners. And we felt that at number three, it gives him a chance to have a matchup against the spin attack."
Gayle top-scored with 13 in his team's disappointing 55 all out in their opening defeat against England on Saturday.
The big-hitter smashed three boundaries before falling to pace bowler Tymal Mills in the lop-sided contest, but Estwick believes his presence in the dressing room is just as important as numbers.
"Chris has been a wonderful servant for West Indies cricket. We still expect great things from him," said Estwick, who is a former Barbados player. "But he also has a lot in terms of addressing the room and helping the younger players."
He added: "Sometimes we tend to just look at performances and we tend to think that the numbers don't match up. But there's a lot more to a cricketer, and there's a lot more to an experienced player."
Gayle has scored 1,867 T20 runs including two centuries for the West Indies.
But the Jamaican star has made just a single half century in the last five years at international level over 27 innings and his inclusion in the World Cup squad was a topic of debate. "What people tend to forget as well is Chris offers a spin option," said Estwick.
"When we played against Australia, Chris bowled really well. So there's a lot of roles that Chris has to play within the team." Skipper Kieron Pollard said "we are backing him to do well" ahead of the tournament and Estwick echoed similar sentiments.
"Just don't look at the performance. Look at in the past, he's done very, very well at the World Cup level," he said. "And I'm sure before the tournament is finished he will do well again."
Talking about their team's six-wicket thrashing to England, Estwick said, "one bad game doesn't make a summer" and remains confident of them bouncing back in their bid to claim a third T20 world title.