Celtic manager Ronny Deila admitted to irritation at his side's tired performance in their hard-fought Scottish Premiership win away to St Mirren.
Celtic ground out a narrow 2-1 victory thanks to a double from on-loan Manchester City striker John Guidetti.
The Swedish striker followed up his strike against Hearts in midweek by bundling home the opener in the 42nd minute.
A terrible throw out from Celtic 'keeper Craig Gordon allowed Kenny McLean to capitalise on the mistake and fire St Mirren level just after the break.
However, Guidetti pounced again in the 63rd minute to rifle a superb pass from Anthony Stokes through the legs of St Mirren stopper Marian Kello to claim Celtic's first win away from home since the opening day.
It was a bitter blow for St Mirren who matched the Glasgow giants for large spells of the game and Celtic boss Deila said there were few positives from the game.
"I feel a bit irritated inside but it's tough to play three games in such a short time and you need to be strong to win on a day like this," the Norwegian said.
"We got the win, that's the most important thing of course, and it was good to come back after losing a stupid goal so that's the positives.
"But I think we looked tired and heavy in our legs. We were always one metre behind in the second balls and we didn't get compact enough.
"On the ball we were taking too many touches and didn't get up the tempo we wanted. We didn't create as many chances as we wanted.
"It was a hard game and St Mirren were pressing hard and had a lot of enthusiasm so in the end I'm happy to win but the performance could be better.
"We have now played three matches in six days which is hard. We haven't changed very much in the team so you get a lot more heavy legs and the players need to get used to it.
"We work hard in training every day and we have to look at everything we do to get as best as possible energy into the games."
Next up for Celtic is a Europa League encounter against Dinamo Zagreb at home on Thursday.
Deila admitted the Scottish champions would need to up their game if they were to pick up a positive result against the Croatians.
"Of course, but it's a different game. It's at Celtic Park and it's always fantastic to see the supporters there.
"The players know this is a huge game so we are really looking forward to it."
The Celtic boss said Kris Commons and defender Jason Denayer, who both missed the win over St Mirren through injury, should return for Thursday.
"Kris has a huge impact in the team. He has slightly pulled a muscle in his upper thigh. We hope he will be back for Thursday, Jason Denayer as well," Delia said.
Celtic remain in fourth place five points behind leaders Dundee United, albeit with a game in hand over the table toppers.
United continued their impressive start to the season with a 2-0 win over St Johnstone while Hamilton held on to second spot with a 4-0 thumping of Motherwell in the Lanarkshire derby.
Inverness remain in third despite a 3-2 defeat away to Aberdeen while Ross County ended a seven-game losing start to the season with a 2-1 home win over Dundee.
Source: AFP
