Russia's Sharapova is currently serving a 15-month doping ban but has been handed a wildcard entry to the Stuttgart event, which starts two days prior to the end of her suspension. The Porsche Grand Prix begins on April 24 and Sharapova is set to play her first-round match April 26 -- her first day officially back in the sport.
Speaking at the BNP Paribas Open in Indian Wells, Wozniacki said: "First of all I think she's a good draw for tennis, women's tennis in general. But two, I think it's questionable allowing -- no matter who it is -- a player that is still banned to play a tournament that week.
"From the tournament side I think it's disrespectful to the other players and the WTA. But it is what it is. Obviously rules are twisted and turned in favour of who wants to do what.
"I think everyone deserves a second chance and I think she's going to come back and fight her way back. I'm sure she's going to play well. But at the same time, I feel when a player is banned for drugs, I think someone should start from the bottom and fight their way back."
Asked to clarify her point on the Stuttgart tournament, Wozniacki answered: "I think once a tournament is started and a player is banned, I don't think a player should be allowed to play that week."
Earlier in the week, Angelique Kerber said it was "a little bit strange for the other players that somebody can just walk on site Wednesday and play Wednesday."
Information from the Press Association was used in this report.