Celtic's
The Hoops will start the second of three qualifying rounds with the visit of Icelandic side Stjarnan on Wednesday night.
Mackay-Steven, who grabbed the only goal of the game in a friendly a 1-0 win over La Liga outfit Real Sociedad on Friday, said: "Friday night was another tough opponent but we are definitely feeling fitter and sharper. It was a good test for us.
"We have been working on a few things in training and have definitely had good work-outs in the three pre-season games. So I'm sure we will be ready for Wednesday.
"It's looking good and looking ahead to Wednesday. I'm excited.
"I came back to pre-season with no injuries, so I'm happy and looking forward to the season. I'm feeling good."