Neil Lennon watched Celtic ease through their Champions League qualifier with a comfortable 2-0 win over Cliftonville at Parkhead but admits they will have to improve next week against Elfsborg.
Goals from defender Efe Ambrose and forward Georgios Samaras made it 5-0 on aggregate and confirmed the Hoops will play the Swedish side in the third qualifier with the first game in Glasgow next Wednesday.
Elfsborg, whose league season is up and running, won 4-0 against Daugava in Latvia earlier in the day to progress 11-1 over the two legs.
Celtic beat HJK Helsinki and Swedish side Helsingborgs in the qualifiers last season on the way to the last 16 which is why Ulsterman Lennon is aware of what is required to make the same sort of progress which netted the club over £20million in prize money.
The Celtic boss, who told Nottingham Forest they will have to improve their reported £1.5million bid for defender Kelvin Wilson if they want to take the defender back to his former club, said: "We had 30 attempts at goal so our shooting wasn't at its best, we were a bit rusty.
"Our back four looked good, it is a couple of clean sheets but we will have to improve a lot for next week.
"We will have to be better with the movement and crisper with the passing and obviously be a little bit more clinical in front of goal.
"Judging by Helsingborgs, if that is a barometer, it is going to be a big step up.
"We will have them watched at the weekend and try to cover everything we can.
"But a week is a long time in pre-season and the players know what is at stake."
The former Celtic skipper, though, is not depending entirely on taking a lead over to Sweden.
He said: "We will try to take the game to Elfsborg and try to put them under pressure.
"A clean sheet will be a huge bonus but this team and these players can score away from home."