KEY BACKMAN Tom Lonergan hopes the umpires won't go too far in their crackdown on interference in marking contests this season.

The AFL's umpiring department has flagged that it will apply more scrutiny to blocking and shepherding in contests, with the changes set to make defenders' jobs even tougher.

"We will have to evolve with the game," Lonergan told

"I know the fans love seeing goals and marks and that type of thing, but defenders need to be able to do something to help their team win.

"You want to play some part of the game rather than just show up and be a witch's hat.

"I can see what they're trying to do, but we'll just have to wait and see what happens."

Lonergan and his Cats teammates will get a first-hand look at the changing interpretations when Geelong takes on Gold Coast in Townsville on Sunday, March 1.

"We'll work through it over the next few weeks," Lonergan said.

Another innovation to be unveiled in the coming weeks is the trial of four field umpires.

Lonergan has mixed feelings about the trial.

"I don’t think it is needed," the 2011 premiership player said. "I don’t think it is needed at all.

"I think three umpires do a good enough job. They're becoming so professional now.

"It's just another person on the field. The AFL was talking about there being too many people on the field – trainers and that sort of thing – only a year ago.

"So I'm not sure if adding another umpire would be the right thing to do."

In terms of his own career, Lonergan is entering the twilight. His recently extended contract expires at the end of the 2016 season, by which time he will be 32.

But after being nominated in the initial 40-man All Australian squad last year, following a dominant season against many of the competition's most powerful and talented forwards, he believes that his best form still lies ahead. 

"I'm still trying to improve," Lonergan said. "I still want to be a better player, a needed player, and have an impact for the team."

Lonergan expects to get plenty of support from Geelong's emerging defenders this year.

"I think Jake Kolodjashnij will get a good chance to show what he's made of and Jed Bews will get more games playing that small defender role," he said.

"Mark Blicavs will come down and help out. So we've certainly got some depth there."

However, this season is likely to mark the end of an era for Geelong's backline, with five-time All Australian half-back Corey Enright set to hang up his boots at the end of it.

"You sort take for granted playing with the same blokes year in year out, but you just enjoy doing it," Lonergan said.

"You know what each other is capable of and you know their strengths and weaknesses.

"We've had a lot of time together and it will be sad when the last day comes, but that's all part of footy.

"We'll enjoy this year and strive to win as many games as we can."