A verb phrase is a phrase that consists of a verb and other words, like auxiliaries, that indicate the tense, mood, or person of that verb.
"would probably have come" is a verb phrase because it consists of the main verb "come", plus the construction "would have" that expresses the third conditional mood, which it's a mood that expresses a situation that could have only happened in the past if a certain condition had been met; and the word "probably" that puts emphasis the idea's certainty expressed in the third conditional.
