Robinson is a safe lock as your RB2. Gibson is unlikely to suit up, and even if he does, Robinson’s workload should be big enough. Edit: Gibson has just been ruled out.
Flex is a trickier decision, though.
Gabe Davis offers huge upside, but virtually has no floor. He is a risky gamble.
Swift is even riskier. In the last 9 games he played, he had 1 strong showing. If you want to gamble, go for Davis, not Swift.
The best option here could indeed be Tyler Allgeier. Personally, I don’t trust the guy at all. But there’s no denying that he had 2 strong showings in a row now, and a perfect matchup against the remains of the Arizona Cardinals.
TL;DR:
Allgeier = better floor, notable upside
Davis = higher upside, but zero floor