SAN FRANCISCO — The Giants released an injury report on Monday that included positive updates on four relievers. Right-hander Joel Peguero has started a rehab assignment and lefty Sam Hentges doesn’t seem far behind. Jason Foley, a potential late-innings option, has graduated to bullpen sessions in his rehab from shoulder surgery. Reiver Sanmartin has started a throwing program after getting hurt in the World Baseball Classic.“It’s weird to have momentum on the injury list, but it’s a good group of arms,” manager Tony Vitello said of the rehabbing relievers before Monday’s game.The Giants didn’t do much to address their bullpen in the offseason, but they always figured they would put a trusted group together at some point. Between the returning arms and the young pitchers who will get opportunities to lock down jobs, they’re hopeful they’ll have solutions, even if there’s some pain early. The question, though, especially after the last 18 innings, is whether it will be too late by the time it’s all sorted out. A day after giving up four runs in the eighth, the Giants gave up four in...