it depends what formation you 're following.In the 30 odd seasons I've played this game I've probably had around 5 main strikers. If they don't average around a goal a game get rid of them.
If playing from the center (4-3-3, 4-4-2 ND) STs must score. If playing from the flanks, just find 2 good wingers and keep your ST scoring every 2nd or 3rd match.