The 25-year-old Hales cracked an unbeaten 116 to give England a memorable group stage victory over Sri Lanka, becoming the first Englishman to score a century in the shortest format of the game.
Having struggled for form of late, averaging under 10 in the LV= County Championship last season, Newell believes Hales suffered after being told he could not participate in the lucrative Indian Premier League.
But now he has seemingly put recent disappointments behind him, Newell wants to see Hales back at his best when he returns to the Nottinghamshire side.
"In terms of four-day cricket we have always used him as an opening batsman," said Newell.
"Trent Bridge has the tradition of being difficult for opening batsmen but to be fair to Alex, last year was the first where he has really struggled in four-day cricket.
"I would put that down to the fact that we wouldn't let him go to the IPL. I think he probably became a bit disenchanted with life having been denied the opportunity to go.
"I'm hoping that this year, once he comes back from the World Cup, he will have a positive attitude to four-day cricket."
Newell also praised the mentality of Hales to come back from a poor spell to produce his best display for some time.
"I think you have to be mentally tough to play international cricket, that is a given," he said.
"But he has put a run of low scores and disappointing performances, for both England and Nottinghamshire, behind him and produced a match-winning innings.
"The major feature of the innings was that he was not-out at the end, he didn't just make 100 and let someone else win the game. He finished the game off himself and that is something he should be proud of."
After losing to New Zealand on the Duckworth/Lewis method, Hales could not have hit form at a better time for England as his scintillating innings keeps Ashley Giles' side in the mix to reach the latter stages.
Next up is another night game - this time against South Africa - and Newell reckons the Proteas will see Hales as the main man to stop if they are to prevent another England success.
"Alex is going to be the key wicket for South Africa to target," he said.
"I'm sure they will have some ideas about how they can restrict him but he is a very powerful player and hits the ball a long way.
"There are other players in the team who can make the difference and with the nature of T20 it is not like you are going to score well in eight to 10 games in a row.
"It just isn't like that with the way you have got to smash it from the word go but he will like to feel he can make another major contribution to help England make the semi-finals."
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