Maria Sharapova should have been given a tougher route back into tennis following her 15-month doping ban, according to Serena Williams' coach Patrick Mouratoglou.
Sharapova returned from her suspension in April but missed the grass-court season after a thigh injury forced her to retire from her Internazionali BNL d'Italia second-round match against Mirjana Lucic-Baroni in May.
The five-time major winner - who had earlier been denied a place at the French Open - will need a main-draw wildcard if she is to be guaranteed a grand slam return at the US Open next month, but invitations to forthcoming events in Stanford and Cincinnati will enable her to make a case for inclusion at Flushing Meadows.
However, while Mouratoglou concedes that the presence of Sharapova on the tour is good for tennis, he is unhappy at the ease with which she has been able to resume her career.
"Be happy because she's great for tennis," he told Omnisport. "All sports need iconic figures and she is, she's a superstar.
"[I am] happy to see her back for the WTA Tour, but not happy to see her welcomed back like players who return from injury.
"Part of punishment should be starting from zero, not receiving a helping hand through wildcards."
Sharapova begins her Stanford campaign with a first-round match against Jennifer Brady on Monday.