India's stand-in captain Virat Kohli believes that Rohit Sharma's dynamism and capacity to build big innings could give India the edge at the 2015 World Cup. A fractured finger had kept Rohit out of the side since August, but he returned to competitive cricket with a 111-ball 145 against the Sri Lankan side in a practice match, and is now set to play in the fourth ODI in Kolkata.

"It's great to have Rohit back, because a player like him, if he gets going, he can be the X-factor in the World Cup," Kohli said. "He can win games for you and get those big runs. We know how lethal he is at the end of the innings. His value to the team is massive."

Kohli backed Rohit to make a brisk return to form, despite the frustration of a layoff that had been twice as long as originally anticipated, due to a complication during recovery. Rohit also provided excellent support to others, in the dressing room, and on the field, Kohli said.

"The good thing about Rohit is that he doesn't really change himself or his game according to successes or failures. That's one of his biggest strengths. Even after such an unfortunate injury in England - going out half way while he's batting well, to get some rest and come back to get a hundred in the first game he plays, shows his mental toughness.

"He brings a lot of positivity to the team. He's a good thinker on the game. In the past when I've been leading the side, I've spoken to him about things that could be done in different situations, and he's always up for discussions about fields, or plans for particular batsman."

Shikhar Dhawan has been rested for the final two ODIs, and his exit will allow Rohit to return to his customary place atop the order, without displacing Ajinkya Rahane. "Most probably Rohit will bat where he's batted in the past for us," Kohli said. "It's all about giving him confidence as much as we can before going into the World Cup. These two games and the tri-series in Australia will really help him come back to his groove at the top of the order. We will be looking at giving him as many overs to bat as possible."

Umesh Yadav has been one of India's outstanding performers in the series, collecting a series-high eight wickets at an average of 16.37. Four of India's fast bowlers, including Bhuvneshwar Kumar and Mohammed Shami, are unavailable for this series, but the attack's ability to pose a menace nevertheless means fast-bowling is becoming an "area of strength" for India, Kohli said.

"Umesh is someone that I believed, if he gets more consistency in his bowling, he'd be right up there with the best bowlers in the world. He's got the fitness, he's got the strength, and he's a naturally strong guy. He bowls at pace, swings the ball, has a rhythmic smooth action, and is a great fielder. He's got everything - just that consistency bit was lacking in the beginning. Now he's much smarter as a bowler. With the new ball his consistency has improved miles and I've been really impressed with him.

"The all out pace attack is something we will look forward to in the coming months. That's an area of strength we want to build as an Indian team, which will be a change of character for us. In the past, we haven't really had two bowlers who bowl 150 plus with the new ball (Varun Aaron and Yadav), and another guy who is 6'4" and can get the bounce (Ishant Sharma)."

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando