England head coach Andy Flower feels the maturity of their One-day side's skipper Alastair Cook will prove vital to team's success in the forthcoming series against India.England will fly out to India Monday with Cook looking to repeat the team's success at home. England play five ODI against India beginning Oct 8 at Hyderabad.Cook's place in the side at one point was questioned, but he proved his critics wrong with prolific scoring this year and then steered his side to an impressive series victory over India.Flower called Cook an 'excellent' leader.'He's been excellent as a leader and grown in confidence,' Flower was quoted as saying in Daily Express.'On the tour of Bangladesh, when he captained while Andrew Strauss was resting, he grew and learned a lot and I'd say we've seen similar growth this summer.'It's always nice to see someone grow in confidence. It's horrible to see anyone lose confidence in any walk of life.'So the opposite, seeing someone grow in confidence, is a really nice thing, particularly for us as coaches, ' he said.