But Jonas says: "Ba is incredible. He has rediscovered his form in front of goal. He is sensational for us.
"For me he really is one of the biggest candidates to become top scorer in the Premier League. Is he better than Van Persie? Right now it's six-five in the statistics.
"Van Persie is a star but Demba is also able to create many problems for defenders and he will do that against United as well.
"If Papiss Cisse can also find his form we have perhaps the best pair of strikers in the Premier League.
"They can be a threat to anyone."