Kelly joined the Terriers on loan at the end of March and scored a first professional goal on his fifth appearance at the weekend.
The 18-year-old has switched from centre-half to full-back - and his talent has caught the eye of Kop legend McDermott.
Ablett said: "I think it's a testament to Martin as a person and a player that Terry McDermott has rung me on several occasions to say they underestimated him - they didn't realise how good he was.
"He's played in both full-back positions and he's come up at the weekend and scored a goal with his left foot.
"He's a very level-headed, sensible young man, and the experience of playing there with a young, innovative manager like Lee Clark and with Terry Mac - he's in good hands.
"The experience will have done him good and we look forward to having him back as a more mature player."
The Whiston-born defender scored the winner in a 3-2 victory over Walsall at the weekend, a strike which also earned him the praise of Huddersfield veteran Andy Booth.
The striker said: "Martin looks a very good player and it would be nice to have him here next season. He's definitely one to watch."
Meanwhile, Ablett is hoping his reserves can get their first league win since January 20 at home to Bolton this evening.
The Reds sit bottom of the Premier League (North) but could leapfrog Wanderers by claiming victory.
Ablett added: "It's an important game - they all are. We spoke to the boys yesterday and told them we've got four games left in our domestic programme, and they're four games we need to win - three in the league plus the Senior Cup final.
"They're all massively important games in terms of monitoring the players."
The second string have just three days to prepare for their league trip to Hull following tonight's game.
Ablett revealed some senior players, including the injured Philipp Degen, could be involved later in the week.
"There may be a couple of seniors come into contention later in the week because they need games," he said.
"Philipp will be looking to play at some stage in the next nine days, and we look forward to having him back and getting him some football."
Ablett welcomes back Jay Spearing and Stephen Darby tonight after they were involved in first-team training ahead of last week's Champions League fixture. However, Vincent Weijl is out with a hip injury.
Whatever side takes to the Halliwell Jones pitch in Warrington, Ablett is hoping for more cutting edge than he witnessed during a 2-1 defeat at the Reebok earlier in the campaign.
"It was a very senior test at the Reebok - they had five or six in there with senior experience," he said. "We could have been three or four up at half-time, but we've been guilty through the majority of the season of failing to take our chances when they arrive."