"He's had a really good five weeks. He looks very healthy, he looks very fast," Harbaugh said. "He beat Jimmy one time and I asked Jimmy about it and he goes, 'Hey man, I think I would have pulled my hamstring if I had chased him right there.' [Perriman] eats up a lot of ground. He's running routes very well and he's catching the ball well, but again, he's got to keep building, keep stacking."