Hubert Davis remains optimistic about the immediate future of North Carolina, but the Tar Heels’ coach admits that frustration is building as the team readies to host Pitt on Saturday in Chapel Hill, N.C.The Tar Heels have lost four of their last five in Atlantic Coast Conference play, and as Davis emphasized, turnovers have been costly.Over its last two games — both losses — UNC has committed 28 total turnovers resulting in 41 points for its opponents. On the flip side, the Tar Heels (13-10, 6-5 ACC) have recorded just 11 points off 14 takeaways.”Unforced turnovers is something that we’ve had a problem with,” Davis said, pointing out the stat after UNC fell 87-70 at No. 2 Duke last Saturday. “Against good teams, that’s just not going to work.”North Carolina has a chance for some retribution against Pitt (14-8, 5-6), which defeated the Tar Heels 73-65 on Jan. 28 after scoring nine straight points to close the game and holding UNC scoreless over the final three minutes.The Panthers, though, have endured their own struggles, losing six of the last eight. They are coming off a 73-57 home loss to Virginia on Monday, when Cavaliers ripped off a 17-0 run early and held the Panthers to a season-low 19 points in the first half.