The St Mary’s side were 21st in the table when Eckert took over in November, but after 15 wins and six draws in 26 matches, they are now sixth.
Saints have also reached the FA Cup quarter-final after beating Premier League Fulham in the fifth round, with Arsenal next at St Mary’s on Saturday.
Football hard-man Dennis, who made 129 appearances for Saints during the 1980s, credited the boss for his role in the turnaround this campaign.
Dennis told the Daily Echo: “I have called him Tonda the tinkerman in the past, and he does like tinkering. It’s very much about stats today.
Tonda Eckert’s side are currently unbeaten in 14 matches (Image: PA)
“I’ve always said you can have as many stats and as much possession as you like, it doesn’t win a game. I’ve never seen a team score playing backwards.
“I think we’ve done it well when we’re 2-0 up, and we’ve kept the ball top up. I think that’s the right time to do it, not when you’re one down.
“I think the big thing, and it took a long time to get there, is getting to the back four. Once he got the back four together, everyone knew their job.
“He’s listened, and that’s great for a young manager. I can only praise him for that. I thought he wanted to play five because it was about possession.
“It felt like it was all about playing the ball out from the back, and we still do it occasionally, but we’re playing more of the long ball beforehand.
“We got found out by decent sides with five-at-the-back. They would put it into the channels, and it causes problems. It wasn’t nice for anyone to watch.
“But now it’s great that he’s got us into a position with the boys where it’s in our own hands, and I’ll tell you what, that is magnificent for everyone.”
Dennis believes changes made to the squad during the January transfer window have also played a part in improving the club’s position this season.
He singled out defender James Bree, who returned from his loan at Charlton, and Daniel Peretz, who signed on loan from Bayern Munich, for praise.
“I think getting Bree back was massive, and we have a new keeper, because all of a sudden, and I’ll tell you what, the keeper is massive for us,” he said.
“Because I’ll tell you what, the defenders are looking behind them, and no disrespect, they were looking behind and they weren’t seeing a leader.
“With Peretz, he’s a leader. You can see that. Even when he makes a mistake, he’s into them, telling them what to do, praising them in the right way.
“He’s made Taylor Harwood-Bellis look like a £30million player. We need to sign him, but if he keeps playing like this, it will get more and more difficult.”