Even at his peak in his Spurs days he wasn’t constantly doing gut busting runs all over the place. I’m not saying he was “unfit” for an athlete by any standard, just he never was much of a work horse and played the game in his head in knowing where to be and having better timing.
Look at say Bruno now, he whacks out 50+ 90 minute games a season up and down the pitch. That was never Eriksen, and dare I say Eriksen didn’t have that style of play in him. But they’re different players with different styles.
And to be fair let’s not have blinders on, earlier in the season he was faded by the 60th minute in a lot of games. He’s 31, let’s not pretend he’s 36+.
Again it’s not really a slight on him, more down to his body rather than his own work ethic.