Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Calum Chambers has no regrets about being denied a loan move and insists Arsenal is the best place to learn – even if he isn’t playing. When Chambers arrived at Arsenal in July 2014, he was pitched straight into the action and made an impressive debut in the Community Shield victory over Manchester City. He never looked back and was named the club's first player of the month. By this point of last season, Chambers had made 20 appearances – which totalled 1346 minutes – and been capped three times by England. This season, however, has presented some challenges. Arsene Wenger is turning him from a right-back into a central defender but he wants that transition to take place at the Emirates Stadium. The Arsenal manager would not let Chambers seek a loan in the window but he is not giving him much game time, either. So far Chambers has only been involved in 324 minutes of the campaign.Calum Chambers has struggled for minutes this season at ArsenalArsene Wenger is converting Chambers from a right back to a centre backChambers is not becoming disillusioned at club despite lack of actionHe will start at the heart of England U21's defence against Switzerland 
 Question:One thing of which Chambers is assured is regular games with _'s Under 21s.

England