Even as a sixth-in-the-rotation guy, Aaron Cook was a less than ideal option.

He went 4-11 with a 5.65 ERA with the Red Sox last season.

He managed a lowly 5.54 ERA over his last three seasons.

He had a decent spring with the Phillies this year, sticking a 3.38 ERA in six games and three starts. But the ground ball guy he was likely signed to be – if it qualified, Cook’s 58.6% percent ground ball rate last year would’ve ranked second in baseball – he wasn’t, and he got just 1.78 ground-outs for every fly out.

Even if he was, to be effective, the defense would’ve had to be solid behind him. No guarantees there.

Cook was also due $1.625 million if he’d pitched in the majors this season.

So the Phillies cut ties with him on Tuesday.

But who now assumes that role?

Not likely Rodrigo Lopez. Considering how he fell apart at times this spring – he was optioned to Triple-A almost immediately after allowing seven runs on eight hits against the Braves on March 18 – it’s hard to envision the Phillies leaning on him unless absolutely necessary.

Barring a move to acquire a veteran, that leaves only their three twentysomething minor leaguers: Jonathan Pettibone, 22, Adam Morgan, 23, and Ethan Martin, 24.

How effective can they be?

Between them, only Pettibone has experience above the Double-A level, and even then, he has only seven starts. Martin, acquired in the Shane Victorino trade with the Dodgers last year, has 48 games and 30 starts of experience in Double-A. Morgan has just six games in Double-A.

Of them, only Morgan had any kind of extended stay or flashy resume (by spring standards, obviously) this big league camp. After holding the Braves to just one earned run on four hits in 4 2/3 innings on March 22, the lefthander finished with a 1.93 ERA, but in just 9 1/3 innings.

Pettibone was roughed up for four runs in two innings in his only appearance, on Feb. 28 against the Braves. Martin threw two scoreless the same day with one strikeout and no walks.

Age alone isn’t why the Phillies should be leery. Cole Hamels debuted at 22-years-old, and had just three starts above Double-A before his debut. Kyle Kendrick broke into the bigs at the same age, and got his first taste of Triple-A two years later, when he was sent to work on his changeup.

Hamels his first year went 9-8 with a 4.08 ERA, Kendrick 10-4 with a 3.87.

It’s just that some (most?) just need more time.

By the time Cliff Lee debuted at 24, he had 19 Triple-A starts and Roy Halladay, 21 at the time of his first-ever pitch, had already hurled 72 in the high minors.

Lee threw in just two games that first year, 11 in his first two combined.

Halladay started just two, and entered Toronto’s rotation full-time the next year.

How much more time do Pettibone, Martin and Morgan need? Tough to say, yet.

With Cook gone and Lopez seemingly buried within the organization, the Phillies will likely need two of them at some point this year. If Halladay is seriously injured or ineffective, that will be sooner rather than later – and maybe too soon for any of the three to step in viably.

The likelihood, then, is that if needed, they’ll be used more like Hamels and Kendrick than Halladay and Lee, and won’t have the luxury of flourishing under late-season callup conditions, where guys can hugely benefit from the limited scouting reports on them and their stuff.

For the guys tabbed as “the future,” life might soon be coming at warp speed.

Unless the Phillies have a move up their sleeves