Rioch still believes his former club are short of a proven goalscorer to challenge for the Premier League title.
"You've got to be scoring around 80 goals a season on a regular basis and I just wonder whether they've got enough strikers at the club to score those goals.
"You look at the midfield, there's some good players there, and they've added a very, very good player. He will make the team better. It's whether they've got the ammunition and the goals to go into the top two."
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