Captain Fahrudin Mustafic wants Tampines Rovers to focus on next month's 2017 AFC Cup opener against Felda United, following the Stags' 2-0 defeat to Philippines' Global FC in an Asian Champions League qualifier on Tuesday.
The Singapore outfit were undone by second-half goals from Ahmad Azzawi and Misagh Bahadoran condemning Akbar Nawas' men to the second-tier continental tournament.
Their AFC Cup campaign will begin with the Causeway battle against Felda on Feb. 21.
"We have a tough AFC Cup group, and we must correct our mistakes and be ready for that challenge," Mustafic told The Straits Times.
"We played well in the first half, and should have gone up. After the first goal, we tried to come back but Global are very quick on the counter and got the second."
Tampines returned to Singapore on Wednesday, and will start preparing for the AFC Cup where they made the quarterfinals in 2016 before losing to I-League champions Bengaluru FC.
The Stags have beefed up their squad with experienced internationals such as Madhu Mohana, Khairul Amri and Daniel Bennett, but could still find life difficult in Group G of the AFC Cup.
Tampines will face reigning Vietnam champions Hanoi T&T, 2016 Malaysia Super League runners-up Felda, and Philippines' Ceres.
They had a disappointing 2016 S.League season to finish behind champions Albirex Niigata (S) after a largely inconsistent showing from former Arsenal and Liverpool winger Jermaine Pennant.
Global FC, meanwhile, will now travel to Australia to face Brisbane Roar in the next qualifying round on Jan. 31.
Should they prevail, a showdown against Chinese Super League side Shanghai Shenhua, headlined by ex-Manchester United and Manchester City forward Carlos Tevez, awaits.