The federal judge who will decide whether lawyers at Quinn Emanuel Urquhart & Sullivan get to pursue an antitrust case against former client Uber Technologies Inc. greeted a lawyer from the firm with extreme skepticism and a flurry of difficult questions Friday.

U.S. Chief Magistrate Judge Joseph Spero of the Northern District of California opened a hearing on Uber’s motion to disqualify the Quinn Emanuel lawyers by raising concerns about the similarities between the lawsuit he’s overseeing and an earlier suit where Quinn played the defense role for Uber. Spero is presiding over a suit where Quinn lawyers represent defunct ride-hailing service Sidecar, claiming Uber effectively priced Sidecar out of the market. In the earlier case, Yellow Taxi v. Uber, Quinn helped Uber fend off claims from a Maryland taxicab company that claimed in 2014 that Uber was illegally sidestepping local taxi regulations.