Tatum will gain weight and muscle, but with only 4 months until training camp, he isn't going to put a ton of weight on. He just played 100 games as a rookie. He'll take some time off to recover then get into a routine. But expecting more than 8-10 lbs of muscle in 3 1/2 months is unrealistic. I think it will take 2 to 3 offseasons for him to put on the 20+ lbs of muscle he will need to be at his peak.