Two nights earlier, the Blue Jackets played perhaps their ugliest game since early February, a lethargic shutout loss that made the Stanley Cup playoffs seem like a far-fetched notion. Only 48 hours later, after a convincing 4-0 win over the San Jose Sharks before 17,771 in Nationwide Arena, the dressing room once again was swelling with confidence and a little postseason daydreaming was permissible. “We’ve had a long winning streak already this season, right?” said left winger Matt Calvert, who opened the scoring with a first-period goal. “That’s how I look at it: Just keep going, just keep playing. We can do something great if we set our minds to it.” The Blue Jackets had tremendous speed again last night, and goaltender Sergei Bobrovsky spun perfection again, making 30 saves for his fourth shutout of the season, all in his past 15 games. James Wisniewski, Ryan Johansen and newcomer Marian Gaborik also scored for the Jackets, who moved within two points of eighth-place Detroit in the Western Conference with eight games remaining. “We all knew Sunday wasn’t up to our standards and our expectations,” coach Todd Richards said. “Tonight it was great to get back on track. “We got back to our style and our identity of playing fast. We defended well. Our goalie made saves when we needed, and we were opportunistic. We played with speed in all zones tonight.” The Blue Jackets have played San Jose twice this season — both in Nationwide — and won by an aggregate score of 10-2. But this one was more emphatic than a 6-2 win on Feb. 11. “We skated in sand, and even worse, we probably had our heads in the sand,” Sharks coach Todd McLellan said. “That’s a bad combination.