Celtic right-back Alistair Johnston believes they can be a “really top team” if they sharpen up in both boxes but he accepts they are running out of chances in the Champions League.

The Scottish champions suffered defeat by the narrowest of margins against Lazio on Wednesday night.

Luis Palma was ruled offside by the VAR officials after thinking he had put Celtic 2-1 ahead in the 81st minute after it was decided that the ball skimmed off the leg of Daizen Maeda on its way to the winger.

Then Lazio got the crucial third goal of the night five minutes into stoppage time after former Chelsea and Barcelona forward Pedro won the ball back and headed home seconds later with the VAR officials ruling him just onside.

Celtic are on zero points from two matches after going down to nine men in an opening defeat by Feyenoord and now face a pivotal double-header against Atletico Madrid, who visit Glasgow on October 25 after beating the Dutch champions 3-2 to move on to four points.

Johnston said: “We still believe. I think we have shown we can play with anyone. That was a top team and we had a lot of spells with the ball where we were comfortable.

“But you need to find a way to turn that into wins because every match, especially when you go away in the Champions League, is going to be difficult.

“Our mind is still on getting out of this group and I still think there’s a chance but this next match becomes all the more important. We know that. You lose again and the ride is probably done.

“We need to really dig in and find a way in these next two games against Atletico to get some points on the board.”

Celtic took an early lead through Kyogo Furuhashi after a penetrating move but conceded an equaliser from a corner.

Johnston added: “We just need to get a little more ruthless in both boxes, in terms of defending our box and set-pieces, and just be a little more clinical.

“If we can add that element in both boxes I think we can be a really top team because we showed in the middle third that we can play with these teams.”

Celtic had looked the likelier team to get in front for most of the second half.

The Canada international said: “It felt really good second half, like we could move the ball around, we were comfortable, breaking through their press. We probably didn’t create as many clear-cut chances as we would have liked but we weren’t really conceding much.

“With the crowd behind us, we always felt like we were going to get one, and it felt like we did with Palma finishing it off.

“That’s football, isn’t it? Sometimes it goes your way and sometimes it doesn’t but we want those ones to start falling our way because it feels like there have been a couple now that have gone against us and we need to find a way to get the win.

“The margins are so slim, one slip and this level of players will punish you. I mean, that’s Pedro with the header at the back post, for crying out loud, from one little thing.

“We need to be extra cautious and that’s part of my role in the Champions League, to be really defensive-minded. There was one moment where I kind of get caught out and all of a sudden they are scoring at the back post. That’s what is frustrating for myself personally and I think for the team as well.

“I would love to say we are going to learn from this and we will but at this stage you just don’t even want to make that mistake, we feel we are past that.

“It’s frustrating but we have to move on and bounce back.”