The Eagles suffered their first loss on Saturday night, with the Sydney Swans lifting in the final quarter to steal a bruising clash by 13 points at Patersons Stadium.
John Worsfold's side passed a credibility test after wins over North Melbourne and Port Adelaide, but Selwood said finishing without the four points wasn't good enough.
"It's very disappointing from where we've come," Selwood said on Saturday night.
"I think we've set a standard for ourselves, so in terms of being proud, proud is getting the wins on the board and making the fans happy and also ourselves.
"That's the standard we've set. It's time and experience and we haven't got anymore excuses."
Selwood said it was particularly disappointing to be overrun in the fourth quarter at Patersons Stadium after outplaying both North Melbourne and Port Adelaide late in the side's first two games.
"Our major strength so far this season has probably been our fourth quarters, and today that definitely wasn't the case," he said.
"I don't know if they were hungrier than us, if it was their mentality to win more, but we'll have a look at the tape and address it during the week.
"There's a few disappointing things that happened towards the end and we'll make sure we get that ready for the Hawks. It just wasn't good enough today."
Selwood, who has been elevated into the Eagles' leadership group this season, won 18 possessions on Saturday night playing a defensive midfield role on a string of Swans opponent.
The 21-year-old said the young Eagles onballers could learn plenty from hardened opponents Adam Goodes (21 possessions and three goals), Jude Bolton (19 tackles) and Josh Kennedy (18 contested possessions and eight clearances).
"They're very strong and very old-fashioned," he said. "They always get the job done and you love to have blokes like that in your team that are always willing to do the hard work.
"Goodes probably came in and towelled us up a little bit towards the end there. That was a big disappointment.
"They're always a tough team to come up against. You always know it's going to be tight and you have to fight for four quarters to get the win.
"We didn't do that today."
The views in this article are those of the author and not necessarily of the clubs or the AFL