His idea of what Blast looks like could all be in his head. Imagine being guy in trouble and some one comes in to save you, that savior will look like a literal God-send to them. He'll probably look like trash lol
My only fear is that One will troll us hard with Blast like he did with every shonen/hero trope/cliché. There are some chance that he teases us a great design from the past but now Blast retired and became some fat ugly lazy shit haha
i though that there is more than the spoiler, but it was not...
Saitama acknowledged by a few class S -> a glimpse of Blast
saitama acknowledged by a few class A or B -> a glimpse of Blast
saitama acknowledged by a few leader Neo heroes -> a glimpse of Blast / Blue start talking
saitama........ Still long long way to...... Haha