Gary Speed believes Wales still have a lot to work on despite an impressive 2-0 win over Switzerland in Swansea.
The visitors were reduced to 10 men for Reto Ziegler's foul on Chris Gunter, before the defender went down under Timm Klose's challenge in the area.
Aaron Ramsey converted the penalty and Gareth Bale added an excellent second, but Wales rode their luck at times.
"I think Switzerland were the best team we've played and they caused us some problems," said Wales manager Speed.
"I knew we had to stay in the game to give ourselves a chance and I was desperate to get in 0-0 at half-time.
"On the other hand I thought we looked very dangerous when we attacked in the first half.
"In the second half there was a couple of decisions where we could have had a couple of penalties before we got one, and there was the sending off.
"So it went our way in that respect but the win was certainly deserved and well earned.
"I thought we got sloppy when they went down to 10 men, the shape of our team I thought we relaxed a bit and lacked a bit of discipline.
"We got wide open and I wasn't too happy with that, and that's something we must learn the next time against 10 men is not to lose our discipline.
"But we managed to get another goal which was fantastic."
Switzerland thought they had taken the lead early in the second half when Eren Derdiyok stretched his neck muscles to nod Xherdan Shaqiri's free-kick into the Wales net.
But the Bayer Leverkusen foward had strayed marginally off-side and was flagged by the referee's assistant, while Valon Behrami hit a post in injury time.
"It was nail-biting a bit towards the end because Switzerland were going forward and they had a couple of free-kicks and corners," Speed added.
"We gave a lot of free-kicks away around the edge of the box and [Xherdan] Shaqiri's got great delivery and I thought that might cost us, and it did with the 'goal' they scored that was fortunate for us it was flagged off-side."
The win saw Wales climb off the bottom of Group G by leap-frogging Bulgaria, who they face on Tuesday under the command of caretaker coach Mihail Madanski following Lothar Matthaus' sacking.
A win in Sofia coupled with Switzerland losing at home the same night to Montenegro, who secured a play-off spot with a 2-2 draw against England, would see Wales finish an encouraging third in the final standings.
"It's going to be tough again to go there, they've got a new coach and any time you go over to Eastern Europe it's going to be a tough game," Speed said.
"We're going to see how the lads are tomorrow and Sunday and plan for Bulgaria on Tuesday."