John Hartson has told BBC Sport that he understands why Adam Matthews decided to leave Celtic and join Sunderland.
Former Celtic striker Hartson has said that he understands why Matthews made the switch from Sunderland to Celtic.
“It's a brave decision from [Matthews], but I'm sure it's all about getting regular football,” the former Arsenal and West Ham United striker told BBC Sport.
"I think if he's not promised that at Celtic and he's guaranteed to play more at Sunderland, then I can understand."
Matthews played for Celtic for four years after moving to the Glasgow giants from Welsh outfit Cardiff City in the summer of 2011.
During his time at Celtic Park, the Welshman won the league title four times and established himself as one of the better players in Scotland.
However, the 23-year-old is not guaranteed a place in the Celtic starting line-up, and it made sense for him to leave.
Although Celtic are one of the biggest clubs in Europe, Matthews will be playing in the Premier League, which is arguably the most popular domestic league in the world and is certainly of a higher level than the Scottish Premiership.