The most basic approach which most academics would use: look at the citations on his papers. Then you could see a lot of the same metrics as in baseball: how his performance has been changing over time, how good he is compared with others in the field, and so on. You could look at his h-index, or at the impact factors of the journals he's been published in. It seems odd that you didn't mention any of these, since they're such a standard part of academic evaluation.