Pakistan coach Mickey Arthur believes new captain Sarfraz Ahmed will bring some much-needed aggression to the limited-overs team which has struggled in the ODI format for the last two years.

Arthur said Pakistan had been playing "a very conservative type" of one-day international cricket. This didn't work "when other teams are scoring 320-340 runs," the South African told reporters on Saturday in the eastern city of Lahore. "We needed to go in a direction that Safi (Ahmed) enjoys playing."

Pakistan is No. 8 in one-day rankings and it can't afford to slip any further by the International Cricket Council's (ICC) Sept 30 deadline or it will have to play in the qualifying rounds of the 2019 World Cup.

Azhar Ali quit the ODI captaincy after Pakistan lost the series in Australia 4-1 earlier this year.

The Pakistan Cricket Board brought in Ahmed, an attacking wicket keeper-batsman, as ODI captain. Ahmed, who already leads Pakistan in Twenty20 internationals, will make his ODI debut as captain when Pakistan takes on the West Indies in an ODI series next month.

The first of four Twenty20s is on March 26. Guyana hosts all three ODIs, starting April 7.

The three-test series begins April 22 with Misbah-ul-Haq retained as Pakistan captain.

Arthur took up Pakistan's coaching post last year. Since then Pakistan has beaten the West Indies in the limited-overs series in the United Arab Emirates while losing to England and Australia.

Players' fitness is another priority for Arthur .

"This is what we are striving for," he said. "It actually starts at the training ground, starts around the attitude toward fitness (and) once you get those, it's easier to get the package in terms of the match."

Pakistan selectors have picked rookie youngsters like all-rounder Shadab Khan and spinner Usama Mir, who both impressed in the Pakistan Super League. They are among 31 players for the training camp for the Twenty20 and ODI series against the West Indies.

All players will take a fitness test before selectors finalise the squad. Arthur said "significant progress" had been made "but we're still not where rest of the world is and that's something that we need to continue (to) work all the time." Arthur was confident that Pakistan, which for security reasons plays in the United Arab Emirates, will face similar conditions in the West Indies.

"Our three ODIs are in Guyana where conditions are going to be pretty similar to what we face at home (in the UAE) so that's good for us," he said. "Spin will certainly play a role and we've certainly got the players to fit the game plan."