DENVER — The Padres arrived here Thursday night with a winning road trip already secured and having just moved into first place in the National League West. They have not won since. And three losses to the Rockies were not even close to the worst of it. Even the best teams stumble on occasion. They move on, often with their best players leading the way. But the Padres will find doing so more challenging after they lost their best player at the start of Sunday’s 8-3 loss to the Rockies. Manny Machado is almost certainly headed to the injured list after spraining his left ankle at the end of the…