Michael Carrick's lone goal was enough to decide the game.
"Galatasaray have got more experience in their team and in the first half we gave the ball away and they counter-attacked well from that," Sir Alex told Sky Sports. "I think [there was a] lack of concentration at times. It's unusual for us to be as frivolous with the ball.
"In the second half we did much better in that respect. I was pleased with the second half - it was more solid, we had better concentration and we saw it out really well.
"They never made any chances and all the chances fell to us - we could have scored four or five in the second half. They were very confident in their play and possession. You get that with these European teams.
"Not a problem; you just have to be patient and make sure that when you're in possession you make it count and with missing the chances we did in the second half, we keep ourselves on the edge."