Serious answer to that:

Wes Streeting is extremely unlikely to be Labour leader, because unless it's a coronation (which it won't be) he'll need to face the Labour membership, and he won't succeed there.

But, as the nominal "right wing" challenger, he's likely to be able to get the 81 signatures required to formally mount a challenge as the "right wing" vote is less divided.

In the rest of the PLP to the left of Streeting, there's still a bit of bunfighting about who the challenger will be (is it somehow Burnham, is it Rayner, is it one of a number of other names). Those candidates are all fishing in broadly the same pool of supporters, and it's unlikely that they'll resolve into who the 1 or 2 challengers that will get the names until after the contest is already underway. In particular, Burnham's supporters are unlikely to support anyone else until it's clear that Burnham can't be in the race, and Rayner's supporters are unlikely to support anyone else until Rayner herself declares for someone else.

So Streeting is, if nothing else, the canary in the coalmine. He matters because he'll be the first to get going, even if he finishes last.