Pedro Beato was sent down to Pawtucket after Friday night's 10-6 Boston win in order to clear a roster spot for Webster.
Webster will be making his third spot start for the Red Sox this season. He's 0-1 with an 11.74 ERA for Boston.
"All the guys made it comfortable from the first start," Webster said. "This third one I've kind of figured out where to go and what time to be where so it's getting a little easier."
As for how he felt about pitching against a Tigers lineup with the likes of Miguel Cabrera and Prince Fielder, Webster said he felt prepared.
"You look at who you're facing and it's guys you've watched all the time on TV," he said. "You just have to go out there and get in a routine and program with your catcher and trust them."