Maguire was left out of the squad which was named by Carsley on Thursday afternoon for the upcoming UEFA Nations League games against Greece and Finland.
The Manchester United defender started in the 2-0 win away to Ireland in their Nations League opener, before being left in reserve for the victory over Finland at Wembley a few days later.
Maguire has only played 17 minutes of Premier League football since the last international window, featuring from the start just twice, against Barnsley and Twente in the EFL Cup and Europa League.
The central defender made headlines on Thursday night though, after his snub from the squad, scoring the injury-time equaliser for 10-man Man United in their 3-3 draw away to Porto.
No additional centre-back was called up instead of Maguire, with Ezri Konsa, Marc Guehi, John Stones and Levi Colwill the four options available in the middle of defence.
Carsley reveals reasons behind Maguire snub
Speaking in the press conference following the publication of the upcoming squad, Carsley gave an explanation of why the 31-year-old was left out.
"It was a chance of having a look at other players. It's nothing to do with form. It's looking at the next two camps to look at other players," Carsley said.
"The players left out all have a case, but we saw the benefit in the last camp of the squad being fresh, feeling fresh and a lot of energy in it.
"It's not just a copy and a paste, I want them to feel like they all have earned their place in the squad. People want to know where they stand long-term, I've told all the players this is a short-term situation."
Carsley has left four players at home who were in the previous squad, with Jarrod Bowen, Eberechi Eze and Tino Livramento also missing out alongside Maguire.
"Harry is a player I've worked with in the past. He was very positive in the conversation we had." Carsley continued.
"It was a case of talking to him about what my decision was, we have some really good centre-backs who we are keen to see play. Harry still has a really important part to play, not just in this squad but also in the campaign.
Carsley seemingly not content with picking the old guard
Carsley impressed many onlookers with how England played in their successive 2-0 wins during the September break, and he was also praised for selecting players he knew well from the youth setup, in what was perceived as something of a changing of the guard.
Angel Gomes, Morgan Gibbs-White, Noni Madueke and Livramento were all somewhat surprise inclusions for the squad in September, and three of the group were handed debuts.
Livramento, the one player who did not get any minutes, has not been included this time, but there was a place for Dominic Solanke, who gets his first call up in seven years, after making a cameo in a friendly against Brazil shortly after he moved to Liverpool in 2017.
Maguire would have been a nailed-on pick under former boss Gareth Southgate, and Kieran Trippier retired from international football after it became apparent he would not be in the new manager's plans.
Ivan Toney has also been snubbed following his move to Saudi Arabia, while a lack of form has seen Eze dropped from the squad picked last month.