"Could Chirinos be there" and "could Kemp run him over" are two different questions.
Chirinos didn't violate the second element of the rule because he had the ball, but Kemp was still allowed to run him over; he didn't violate the first element.
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therefore no blocking of the plate
He was blocking the plate. He just didn't violate the rule.
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Unless the catcher is in possession of the ball, the catcher cannot block the pathway of the runner as he is attempting to score.
But Kemp didn't violate the rule, either.
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If a catcher blocks the pathway of the runner, the umpire shall not find that the runner initiated avoidable contact in violation of this Rule 6.01(i)(1).