"None of us cared about football," said Robertson.
The defender explained that the emotional impact of the accident significantly disrupted the team's planned pre-season physical preparation.
"Pre-season is used to get you fit and things like that. The manager and the coaches couldn't really do that," said Robertson.
Robertson described the difficulty of maintaining performance standards while serving as a source of distraction for grieving supporters.
"We then start the season really well in difficult circumstances because as footballers you've got no option.
The players have to continue because everyone still wants to see a Liverpool team on the pitch," said Robertson.
The emotional toll eventually affected the squad's tactical consistency on the pitch throughout the competitive football league season.
"We then become inconsistent and I think that has a big part to play in it," said Robertson.
Robertson refused to use the off-field tragedy as a definitive justification for the club's current fifth-place league standing.
"We have let ourselves down this season and we're not hiding away from that fact," said Robertson.
The defender pointed out specific deficiencies in competitive intensity that hindered the team's campaign goals. "Our performances haven't been good enough at times.
Our consistency hasn't been good enough, our aggression, determination - everything that makes a Liverpool team," said Robertson.
Robertson recalled how former manager Jürgen Klopp motivated the squad to recover after losing the 2018 Champions League final to Real Madrid.
"This is just the start of our journey. We'll be back here next year," said Klopp.
