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Simulated games are used to replicate on-field scenarios, and while balls and strikes are called, fielders are not used. Hits and outs are instead estimated based on where the ball goes. Prospects Rowdy Tellez and Richard Urena were among the hitters who faced Estrada.
"This morning it was so-so, but once I got moving and got out there and started throwing, I felt much better," Estrada said. "I don't think the back's going to be an issue anymore. It's now just getting the feel for every pitch. I'm still off, you know."
Estrada has slightly more than three weeks to get ready for the start of the season. If he needs a little bit more time, the club could opt to go with a four-man rotation for the first week of the season because of an off-day that follows the season-opening series against Tampa Bay.
The 32-year-old is expected to throw an inning or two on Tuesday, but it's possible that will take place in a Minor League setting. After that, he will settle into a routine of pitching every five days as he builds up endurance for the start of the regular season.
"I'll be ready, for sure," said Estrada, who went 13-8 with a 3.13 ERA in 34 appearances last season. "I don't want to miss any starts. I think I'll be ready. I don't know where my pitch count's going to be. The first two, three times out I may not be at 100 [pitches] yet but if I can just get out and give the guys some innings, that's all I really care about."
Gregor Chisholm is a reporter for MLB.com. Follow him on Twitter @gregorMLB and Facebook, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.