Mitchell Johnson says the impact of Phillip Hughes' death played a part in his recent slip in pace.
Johnson's typically savage speed dropped off during India's tour of Australia last summer, and was more pronounced during the left-armer's Indian Premier League campaign and recent West Indies Test tour.
He admitted the shock death of Hughes last November had contributed to his slide in form.
"I'm not someone who makes excuses, but we went through a bit of a time just before that with Phillip Hughes and that was something very difficult, and it was really hard to sort of deal with it at times," he told the ABC.
"We were definitely under-prepared at that time and my pace was definitely off.