Said the Argentinian, who led the team to two of the last four Champions League finals: "I wouldn't say it's a failure".
Are there any other restrictions? That means Chelsea can not draw Roma, Manchester United can not be drawn to play against Basel and Tottenham will not be up against their Group H opponents Real Madrid.
Teams that already met in the same group or are from the same country can not be drawn against each other on Monday.
Having finished the 2017-18 A-League season in third place, Brisbane Roar will take part in a preliminary playoff against either Shan United of Myanmar or the winners of the Philippines Football League (who are yet ot be determined) in late January, before facing Tianjin Quanjian for a spot in the group stage.
Cahill won the European Cup in 2012 with Chelsea, who remain the most recent English team to make the final.
"In this case, we know we could play Barcelona, PSG or Besiktas".
In other Group matches, Real Madrid beat Borussia Dortmund 3-2, Tottenham thrashed Apoel Nicosia 3-nil, FC Porto beat Monaco 5-2 while NK Maribor and Sevilla drew 1-all.
Tottenham: Bayern Munich, Juventus, Basel, Spartak Moscow, Sevilla, Shakhtar Donetsk, Napoli, Porto or RB Leipzig. As a result of these restrictions, the Blues would only be able to draw three teams in the round of 16 - Barcelona, Paris Saint-Germain or Besiktas.
The draw for the round of 16 takes place at UEFA's headquarters in Nyom in Switzerland on Monday. The last 16 games will be played on the 13th, 14th, 20th and 21st of February and the second legs will be played on the 6th, 7th, 13th and 14th of March.