Defending ODI world champions India play the hosts in the first game here tomorrow.
"The World Cup is coming up and you need to try a lot of players. I think it is a good opportunity for youngsters to do really well in this series and see how it goes in upcoming matches," he said.
Raina tried to defend the squad he has been given for the series.
"I don't think they took the series lightly. The England tour is coming up and so few of the players are rested. If you look at the side, all the players have done well in the IPL and first-class cricket."
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In Raina's squad, Ajinkya Rahane, Ambati Rayudu and Amit Mishra are the only ones to have played in India's last 50-over game against a full member.
Players such as Cheteshwar Pujara, Kedar Jadhav, who has had a good IPL-7, and Manoj Tiwary were seen toiling hard during the training session.
"Some players are coming back to the Indian team, some are getting their chance to play. It's important to stick to together," Raina said.
"It is a short tour for us, seven days, three one-dayers and no gaps in between. You have to plan very well and work really hard."
During practice, coach Duncan Fletcher conveyed he would like five minutes with all the new boys.