Melbourne, Jan 17 (IANS): Indian captain Mahendra Singh Dhoni Saturday said pacer Ishant Sharma and all-rounder Ravindra Jadeja are not fit for the team's opening game in the ODI tri-series against Australia at the Melbourne Cricket Ground (MCG) here Sunday.

Dhoni said the tri-nation series against Australia and England will be a preparation ground for India's World Cup title defence.

"In this series the most important thing for us will be to get the combination right for the World Cup," Dhoni said ahead of their first match of the tri-series.

"At the same time we will ensure that we don't push the players who have minor niggles so they don't end up being major injuries. We will give them the extra time because we want every player to be at least 80 to 90 percent fit going into a game."

Of the players with niggles, Ishant Sharma (left knee) and Jadeja (left shoulder) will not be available for selection for the MCG ODI.

"There are quite a few players with a bit of niggle here and there and we are monitoring their progress. In tomorrow's game, Ishant and Jadeja are not available for selection because we are managing their workload."

Speaking of his bowling plans, Dhoni wants his pacers to perfect their yorkers for the limited overs challenge.

"The execution of yorkers and bouncers becomes very crucial and that's what we have been working on in the last few days. The bowlers are doing pretty well with the yorkers and if they can replicate in the match, we will be very happy with it," Dhoni said.