If so, yea you can, but Tunnels are more special then that. A Worker could connect to a normal origin and act as a reverse proxy.
Cloudflare -> Worker -> (Logic) -> Normal Origin, established connection inbound over 80/443
Tunnels connect outbound to Cloudflare. So unlike with a normal origin, you don't need to have a static IP, or port forward, or worry about https. The tunnel creates a secure tunnel/connection back to Cloudflare's edge, as an outbound connection. Then when requests come to Cloudflare's proxy for the tunnels' hostname, CF just forwards the requests down the tunnel, and cloudflared (the actual service running on your infrastructure) connects to your configured web server
Cloudflare -> Tunnel Connection -> cloudflared (running on your server) -> Web Server