Steve Clarke defended his change of system after Scotland 's 1-1 home draw with Israel at Hampden Park.
The home side broke the deadlock a minute from the break with a Ryan Christie penalty but Eran Zahavi fired in the deserved equaliser in the 73rd minute with Scotland left to reflect ahead of the away game against the Czech Republic on Monday.
Clarke, who said there was "a lot to like" about debutant striker Lyndon Dykes' performance, said: "Obviously the result was disappointing, especially after being in front.
"We went to sleep on a throw-in in the second half and got punished.
"Not a lot of chances in the game, there were some good things and things we have to work on.
"But when you take into consideration it was three training sessions I thought the good outweighed the bad.
"I thought the system worked tonight as well. As a coach you always want to have a couple of systems up your sleeve, you want to be flexible in-game and flexible between games.
"Some games a back four is better than a back three. Obviously Israel play with a back three and I thought tonight was a good chance to look at playing with a back three and I thought we did okay.
"As I said there was a lot of things we have to work on, we have to get better, especially offensively but the defensive work, the way the team shaped up was decent.
"I thought the back three we were good, Scott McTominay, Scott McKenna and Kieran Tierney did well.
"The two wing backs were fine. Whether it is the system going forward all the time, we will have to wait and see. Every game is different. If we can do it and well it is a good system to play.
"It was a pretty even game and draw was probably a fair result."
Israel boss Willi Ruttensteiner, who will bring his side back to Hampden for the play-off semi-final next month with both teams offered the chance to reach the finals of Euro 2020, said: "We take the point and it is a good beginning to the campaign from our point of view,
"Especially in the second half I think we played better but I was not satisfied and at the end I think 1-1 was correct.
"We showed good technique and moved the ball well and showed we could play football. For us, it was a small success and a good start."