Swans fell to Cardiff City in yesterday's derby.
Trundle told talkSPORT: "We've shown flashes of what we can do but then there is another side where we haven't looked ourselves.
"We do switch the squad around for the Europa League games and then the Premier League match after but it can affect you. It's shown in our form a little bit."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball