However, Lampard's side were second best in the first half, with the Blues boss making three changes at half-time – Barkley being one of the alterations.
Mason Mount, Billy Gilmour and Reece James were the players to make way, but Lampard insists he has full confidence in the young trio.
"The first half wasn't what we're used to in terms of performance this season," Lampard, who took advantage of the temporary rule allowing five substitutions, told a news conference.
"We seriously lacked urgency and intensity in the first half, so the three subs... I probably could have made more subs or different subs.
"Of course, if we didn't have the extra subs, I wouldn't make the three at half-time, but the reason the subs are here is because they are trying to prevent injury and understand that the players have missed a proper pre-season.
"We can probably look at that we had three big games in a week, a very difficult game on Thursday, so I'll allow us a bit of credit, and the fact they showed enough to turn it around against good opposition.
"I don't think we have played that badly this season in 45 minutes; we played a lot better and lost games. So when it looks like I'm criticising, I'm actually positive that it's not the norm for us but it felt like it had to be addressed.
"I could've made different changes as well. In Mason's situation, he played two games in a week and gave a lot of input against Man City. Reece James hasn't played in a long time since going into lockdown and Billy's the same, so there are contributing factors around it.
"They are going to be top players, they will have top careers in football - that's the players they are - so whether you can call it a learning experience, I did do that.
"They are all good lads, they train well and I've never had a problem with them at all, so I've got no worries."
One player who did draw Lampard's praise was goalscorer Barkley, who has looked sharp since the resumption of the campaign.
"I played with Ross and I know he's a great lad. He wants to be the best player he can be and has a great attitude," Lampard added.
"Before lockdown, he put in some really good performances for us, his attitude has been spot on in training, he looked after himself in lockdown, and he was unfortunate not to start against Aston Villa. Since then, he's made an impact in every match he's played.
"I've got lots of time for Ross. He's a big player for us - you saw that today and in the last three games."