Just have a frank chat on the lines of "dude, i hate to say this but we are not delivering. We have to change our ways a bit. Here's a list of things I need in the next two months: you have to nail one each week. I don't care which one, just give me one each week. I ask you because I trust you can do it, I think you have more potential than others. We just have to get something to show, y'know? If that doesn't happen they'll come down on me and make life hard for everyone; but if we show we're running full speed, we become heroes and will have larger buckets when money rains." For extra safety, give him a list 30% to 50% longer than necessary, and review it with him right there to let him drop a few of the scariest items and still have enough to cover the planned timestamp. He will feel a bit more involved in choosing his own destiny.

There is a chance the guy will bolt for good shortly after: this would mean he hated the place already, good riddance. If he stays on and improves his ways, the challenge is on you to keep finding realistic week-long targets, or you can relax it a bit and have two or three-weeks targets instead.

Extra-bonus: have this meeting on Tuesday morning, starting the system the following week. On monday he will hate you, from Wednesday on his morale will suffer; and it gives him enough time to clear any competing interest (either professional or private).