Robert Shapiro, who defended O.J. alongside Robert Kardashian, tells us Kim has what it takes to become a sensational lawyer. And, once she passes the bar ... the door's open for her at his law firm.

Shapiro was leaving E Baldi restaurant in Beverly Hills Wednesday when he broke it down for us ... he says Kim's already done incredible work with no experience, so the sky's the limit now that she's seriously practicing law.

He makes it clear she has a long, difficult road ahead of her and there's a high chance of failure ... but Robert believes she'll pull through.

In fact, Shapiro says it won't take much for her to surpass her father's lawyerin' skills -- a not-so-subtle dig at how much Kardashian actually contributed, strategy-wise, to Simpson's defense.

As we reported ... Kim's been studying hard for the baby bar exam and was hitting the books earlier this week for a torts essay with attorneys Jessica Jackson and Erin Haney, with whom she's apprenticing.

She says she aced it, by the way ... and don't count Shapiro among the doubters.