Bears rookie running back Tarik Cohen was counting on the Falcons’ defense to overrun his toss play. Its speed, while valuable, can cause it to do that. And then Cohen would burn them with his. ‘‘Atlanta has a very fast defense,’’ Cohen said. ‘‘I had beat them on the first toss. So when we got another toss, I saw that they were heavily overpursuing, so I tried to cut back. It went the right way.’’ That’s because it went for 46 yards. On a toss play to his left from the Bears’