In his first game as a 49er, Jonathan Baldwin was everything A.J. Jenkins was not.For one thing, Jenkins is small and fast; Baldwin is big and fast. Jenkins had trouble getting open in two preseason games for the 49ers; Baldwin made two catches in his Niners debut, a victory over the Minnesota Vikings Sunday night.Jenkins, in his debut for the Chiefs against the Steelers, was targeted once and had zero catches.Now, with the 49ers preparing for their fourth and final exhibition game Thursday night in San Diego vs. the Chargers, Baldwin already appears to be an upgrade over Jenkins.The swap of former first-round picks makes the 49ers receiving corps appear a bit deeper and more dynamic heading into the regular-season opener Sept. 8 vs. the Green Bay Packers.Baldwin pulled in a Colt McCoy pass for 19 yards that McCoy said Baldwin made a nice adjustment to grab. He also caught a 4-yard pass from McCoy that was thrown low and behind him.Overall, the 6-foot-4, 230-pound Baldwin played 23 snaps and was targeted three times, catching two balls – just days after being traded by the Chiefs for Jenkins."He's had a nice command of the offense," head coach Jim Harbaugh told reporters...