He realised he hadn't played with half the team.
The side had undergone such a transformation in the four months since he hurt his knee against Port Adelaide he felt like he was pulling on the boots with a bunch of strangers.
It wasn't an unreasonable thought.
Five players had made their debut for the Lions since round four, when he went down, and just 10 of his teammates were alongside him in both round four and round 23.
One of the additions was fellow ruckman Stefan Martin - who had revived his career to such an extent when Leuenberger (and Trent West, who had a knee reconstruction) were missing, the club signed him to a two-year contract.
Leuenberger said he was excited by the prospect of playing alongside one of the League’s most improved players.
"I wanted to see how Stef and I would go," Leuenberger told AFL.com.au after the Lions suffered a 62-point loss to Geelong on Saturday night.
"In my eyes he is the best ruckman in the League and I just wanted to see how I could adapt to suit the way he is playing and I think tonight was pretty positive."
That positive assessment was one shared by the coach, Justin Leppitsch, who was pleased with what he saw.
"We obviously used them more as a midfield combination tonight rather than ruck and forward but I think there is something to work with there," Leppitsch said.
Leuenberger had 36 hit-outs and 11 disposals while Martin had 31 disposals and kicked a goal to once again be among the Lions' best players.
Given the limited lead-in time, it was a performance to give Leuenberger confidence for the future, particularly he said with West to return too.
"We only had three days to prepare for it," Leuenberger said. "Obviously the chemistry has a long way to go – we only trained five minutes [together] – but I'd like to think if we put a summer into it we'd be pretty dangerous."
Leuenberger-Martin. It sounds imposing enough.
The Lions might have a ruck combination to cause opponents some concerns.
