"Of course it's a great series win," he said after the fifth ODI in Kolkata. "But our fast bowlers could not bowl 10 overs in many of the matches and we have to realise that's where we have to get better. It's good to have guys bowling quick but they also need to be able to keep the runs down and not give away a boundary an over.
"Even though we've won at home, we need to realise that when we go abroad there may not be as much turn for our spinners and so we will not be able to win if our fast bowlers don't bowl well. In other countries our part-timers may not be as effective as they are here."
The series win comes just a month after India were thumped in both the Tests and one-dayers in England. Dhoni said the criticism his side received after that tour did not worry him as he knew Indians were passionate about cricket and bound to react to a loss.
"It happens: you are appreciated when you do well and that should be taken with an open heart. I was not too worried about criticism. We know cricket is big in India. It's a part of our life."
India went into the ODI series against England with several senior players missing through injury, and Dhoni said while the influx of young players helped sharpen the fielding, the seniors were still needed. "It's difficult to replace the seniors talent-wise. But these youngsters have clicked as a unit. They are slightly better fielders. They may save 8-10 runs which matter in ODIs. They have reacted in the right way and been patient in waiting for opportunities to turn things their way. But we really can't really replace Sachin [Tendulkar], [Virender] Sehwag and Yuvraj [Singh]."
Dhoni was named Man of the Series after scoring 212 runs without being dismissed in the five games. He said that he would not be moving up the order, though, since he had adjusted his game to batting in the middle order. "The format of the game has changed. Now, with the Powerplays split, the situations are different. We have to be good at the slog overs and rotate strike as well. I have changed my style of batting. At No. 3 you can be flamboyant but at 5 and 6 you have to be careful."
India will play a Twenty20 international against England in Kolkata on October 29 and the organisers will be hoping for a larger crowd after disappointing turnouts over the one-dayers. An overdose of cricket and the absence of some star players were the reasons Dhoni pointed out for the empty rows in the stands at Eden Gardens. "We have played a lot of cricket in India: the World Cup, IPL and then the Champions League T20 were held here. Big stars like Sachin were missing from this series. This is also one of the biggest stadia in India so it's not easy to get a jam-packed crowd every time."