"It was our season in 90 minutes - very good at times, bad on occasions and then just bad," said Souness after the game at Ewood Park.
"Bolton boss Sam Allardyce must be delighted because at 3-1 up we were looking to control things."
"To be 3-1 up just before half-time we really fancied our chances. But they scored at half-time and then the initiative was with them. That goal was vital for them.
"We did not defend very well. We were beaten by the simplest form of attack - just lumping the ball forward for the strikers. That is why we lost the game."