Stanislas Wawrinka and Marin Cilic tasted success at the Australian Open and the US Open in 2014, making the most of problems suffered by the likes of Andy Murray and Rafael Nadal.
The latter pair struggled with injuries and loss of form throughout the season, with US Open finalist Kei Nishikori, Milos Raonic and Tomas Berdych also enjoying strong campaigns as well as first-time slam winners Wawrinka and Cilic.
Raonic and Berdych made the semi-finals of Wimbledon and the Australian Open respectively, with the 23-year-old Canadian also making the quarters of the French Open in his breakthrough season.
And former US Open champion and world number one Roddick - who retired in 2012 - believes the past 12 months have seen a shake-up at the top of the men's game, something he expects to continue.
"I think the shake-up took place this year, in a big way," said the American, who is preparing to feature in the ATP Champions Tour event at the Royal Albert Hall in London.
"We always like to point to the young guys but [look at] Wawrinka breaking through and Cilic breaking through.
"If you're anybody in that top 16-18, you're going 'okay, the top guys still have a hold on the game but maybe it's a little bit of a looser hold'.
"With Roger [Federer] and Nadal, they're going to have to start prioritising their events a little bit more. I think the days are past when they'll win 80 matches in a year, because I don't think it would be smart for them to win 80 matches in a year.
"I think the days when it was the top two then three, then four - I don't think you can define it with a number anymore. Maybe tiers, the top tier, then the next five or six guys who are all equal as far as winning.
"I think the shake-up happened this year and will it continue? It probably will a little bit."