The Pies are third on the ladder with a 4-1 record, and have only youngster Sean Rusling - who is recovering from a collarbone injury and should be available in four weeks - on the casualty list.
McKenna says the fact the players are enjoying such good health plays a large part in the confidence of the group and the recent success of the club.
"The players are in good nick, they're healthy and I think that has been the difference in the past two years," McKenna said at the club's recovery session one day after the Magpies' 41-point win over Port Adelaide.
"The players are up and healthy and certainly their skills are improving. We can certainly still improve, but we are certainly winning the games we need to win."
McKenna also agreed the in-form players at Williamstown are forcing the senior 22 to contribute from week-to-week and that the 'pressure from within' was ensuring consistent individual performances.
"Everyone is healthy and playing some good football so it makes the players that are in the 22 perform at their best because they know that at a wink or a blink, the could be out of the side," he said.
McKenna said there were a few senior players and a handful of youngsters in the mix to push for selection should the opportunity arise in coming weeks.
"Rhyce Shaw is coming off his knee, he's impressed in his two-and-a-bit games back and keeps knocking on the coach's door, luckily he's not knocking on my door but he's knocking on Mick's door," McKenna said.
"Players of that ilk … Blake Caracella - who's missed the last couple of weeks - he's a quality player, Shane Wakelin has missed out due to match-ups, he's gone back and as you can expect, performed and his attitude is fantastic.
"Some of the young kids are certainly pushing their names forward too and that's good at this stage of the season."
