Boston College will host Louisville in a matchup of Atlantic Coast Conference teams hoping to return to the winning track on Friday in Chestnut Hill, Mass.The Eagles (4-3, 1-2 ACC) have had peaks and valleys throughout their back-to-back losses at Virginia and Virginia Tech, including turning the ball over three times in each. In last Thursday’s game, which followed a bye week, Bill O’Brien’s team trailed 28-0 before a second-half comeback by the Thomas Castellanos-led offense fell short.”These are tough games, right? All of them are tough,” O’Brien said. “We have to limit our mistakes. … If we can limit our turnovers, penalties, stop the run better, obviously we’ll be in these games. If we don’t, we won’t.”The Boston College defense allowed 532 total yards last week, but this season has intercepted nine passes — one more than its total from all of last season. Cameron Martinez added to that latter total last week while posting a fumble recovery and seven tackles, including a sack and two tackles for loss.However, the status of a defensive anchor in linebacker Kam Arnold (40 total tackles) is uncertain after he was spotted in a sling at practice earlier this week.”I think that sling is kind of a precaution,” O’Brien said. “I’ll probably know more in a few days, but that’s probably a day-to-day deal.”Louisville (4-3, 2-2) opens a three-game road swing after falling in a 52-45 Saturday shootout against Miami. The home loss came despite the Cardinals accounting for 400-plus yards of total offense for the fifth time this season.