City are out of the Champions League at the quarterfinal stage after Wednesday's 1-1 draw.
Dias said: "I don't know what to say. Frustrating. We dominated the whole game. You go to penalties. The effort was there. We had chances. It's a difficult one to take.
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"You always end up doing everything to try to avoid penalties. That's what they wanted.
"The team was there. We fought, we had our chances but it wasn't our day.
"We had the chances. Sometimes the ball goes in, sometimes it doesn't. Now we have to look forward at what's to come in the season.
"We won't have much time to rest. It's a busy part of the season. Now is a time to be strong especially in the head. We're still in two important competitions."