"We'd rather keep everybody on line and not start doodling around with that, especially this early in the year," Mackanin said before Friday's tilt against the Nationals.
The manager also mentioned there will be a new starter Tuesday, though he did not name who that will be.
Buchholz left Tuesday's loss to the Mets with an injury that was later diagnosed as a partially torn right flexor pronator mass. As of Wednesday, the 32-year-old was to seek the second opinion of Dr. James Andrews.
• It was just one appearance, but Mackanin liked what he saw from right-handed reliever Luis Garcia in Wednesday's 5-4 loss to the Mets. In his first outing of the season, the 30-year-old threw a clean inning as he utilized a fastball that hit 98 mph and a 90 mph splitter.
"I was happy to see that," Mackanin said. "He's been given multiple opportunities [in previous years]. That was a good showing.
"He looked relaxed. Granted, it was a lopsided game [at the time], but he looked more relaxed. We're hopeful he's gonna reach his potential this year."
Garcia started the season at Triple-A Lehigh Valley, but he was added to the 25-man roster once left-hander Adam Morgan was sent down following a rough outing. After an uneven 2016 campaign, the Phils will count on the veteran reliever to produce in lower-leverage situations.
"[It] boils down to command, control," Mackanin said. "You pitch ahead, [you] put 'em away. He's got the stuff to do it."
• An issue that plagued the Phillies' offense throughout 2016 was the team's impatient approach at the plate. Last season, the Phils finished 29th in team on-base percentage at .301, including tallying just 424 walks -- also good for 29th.
It's early in the 2017 campaign, but so far there are signs that Philadelphia's lineup is taking steps to improve on working counts and grinding out at-bats.
"The key is to do that the entire year, so I'm not going to get overly excited," Mackanin said. "I'm encouraged by the fact that we look a little more selective at the plate."
Entering Friday, the Phillies were ranked 11th in on-base percentage at .322 and 12th in walks with 34. A good start for sure, but Mackanin needs to see more to be convinced his club's approach has changed for good.
"The test is if you can do it over the course of a season," he said. "I'm encouraged, but cautiously optimistic."