LAKE BUENA VISTA, Fla. -- Newly-signed Phillies ace Jacob Arrieta threw his first bullpen session in a Philadelphia uniform Wednesday, and told reporters that he hopes to make his debut in a Minor League game on Saturday.
Arrieta told media members in Clearwater, Fla., that he expects to throw around 50 pitches on Saturday. It's not entirely clear if Arrieta will face Phillies Minor Leaguers or those from another organization. Following Wednesday's 5-3 loss to the Braves, manager Gabe Kapler said Arrieta will take two days off and pitch either a simulated game or live batting practice session Saturday.
The Phillies have made clear that Aaron Nola is still their Opening Day starter, but the team is understandably eager to see Arrieta in game conditions after signing him to a three-year, $75 million contract.
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"The sooner we're able to get him out there, the better chance we have of Jake being ready to start the [regular] season," Phillies general manager Matt Klentak said. "At the same time, this is a significant investment for a long stretch of time. We want to make sure we do the right things to keep him healthy. We don't want to rush into this and put him in a tough spot."
Because of days off early in the season, the Phillies won't need a No. 5 starter until April 11.
"That gives us some flexibility to work Jake in whenever he's ready, without needing to rush things," Klentak said. "There's a possibility he could pitch on the first turn through the rotation. There's a possibility he could have some sort of a piggyback start. There's a possibility he could [not pitch] on the first time through the rotation and slot back in on the second time.
"We don't have enough information yet, but our goals are aligned with Jake's, which is to get him out there as soon as we can and start winning ballgames."

When asked about Arrieta's decreased fastball velocity in 2017, Klentak said the team's research and development group "spent more time on that subject than anything else this entire offseason."
"There are just so many factors that go into signing a player," Klentak said. "Obviously, fastball velocity and the quality of a pitcher's stuff are among them. But another component is how competitive they are, and we've all seen how tenacious Jake is on the mound. There's also the ability to sequence pitches and be smart on the mound.
"This is not the first time in baseball history that a pitcher has lost some velocity as he's aged. It's happened to a lot of pitchers who have remained successful. It comes down to how smart they are on the mound and their ability to outthink hitters, as much as out-stuff them. He's in as good of shape as any player in baseball." 

Kapler stayed in Clearwater to watch Arrieta's throwing session before driving to meet the team for Wednesday's game.
"Excellent first 'pen," Kapler said. "Watched it from behind. I think he threw 42 pitches. He demonstrated a pretty nasty cutter, but also a fastball that looked like it had lead in it. A lot of finish. I was thinking, 'What would it be like to be a right-handed hitter in there right now?'
"Dangerous. Body language was excellent. Posture was excellent. I've had a couple conversations with him so far that have blown me away."
Lively still in starting discussion
Ben Lively, who allowed three earned runs over five innings Wednesday, remains in competition for a Major League rotation spot -- although Arrieta's arrival could mean Lively returns to Triple-A.
"I thought Lively was good," Kapler said. "He attacked the strike zone with his fastball. He's a guy that's going to fill up the zone. He's going to throw strikes. He's going to induce contact. He did that. He made one mistake [on Preston Tucker's home run] that he knows he made. If he was standing right next to me, he would say, 'I'd like to have that pitch back.' But I thought he did a good job."
Klentak said Arrieta and Nola are assured of rotation spots, but decisions have not been made regarding the final three spots in the rotation. Klentak said right-handers Nick Pivetta and Vince Velasquez have shown "electric stuff" in their Spring Training performances. Jerad Eickhoff, who threw 197 1/3 innings in 2016, has the steadiest Major League track record among the Phillies' young arms, with the exception of Nola.

Up next
The Phillies are off Thursday before resuming Grapefruit League play with split-squad games Friday at 1:05 p.m. ET. Velasquez will start against the Blue Jays at Spectrum Field in a game available on MLB.TV. Pivetta will travel to face the Tigers at Joker Marchant Stadium in Lakeland, also at 1:05 ET, in a game available to follow on Gameday.
Thursday is the Phillies' final day off until March 28, the day before the regular season begins at SunTrust Park in Atlanta.