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The Padres’ grueling stretch of 18 games in 18 days ends today. Finally, an exhale.

Soon, a major boost, too. At some point this week, they seem likely to add Fernando Tatis Jr. back into their already potent starting lineup.

Tatis has been taking at-bats at the team's Spring Training complex in Arizona for almost a week now. It seems likeliest he would skip a rehab stint all together.

Soon enough, it'll be time to pencil Tatis into the lineup. And it should be quite a lineup. As one Padres evaluator put it to me yesterday when I asked around about that lineup: "Someone has to hit seventh, who normally hits second, third or fourth."

That’s the type of lineup problem good teams have. Still, it’s a problem worth solving. So let's lay it out. What will the Padres' lineup look like when Tatis returns? Here goes:

What's the goal?

It's September. The Padres are through the Dog Days. They're in the midst of races for the National League West and Wild Card. They have five off-days over the final four weeks, meaning they can use regular lineups without overworking their starters.

Which is a long way of saying: These should be the Padres' best lineups on a nightly basis. These should be the lineups the Padres would use in the postseason. So, first thing's first:

Where's Tatis?

Before his injury -- a stress reaction in his right femur -- Tatis had batted second all season. It's an optimal spot for a hitter like him. Tatis is clearly capable of wreaking havoc on the basepaths (even if he stopped doing so while playing through injury). And he's one of the team's best hitters.

Given the season Jurickson Profar is having, however, there's a case for dropping Tatis to third. Profar struggled immensely in August. But despite hitting .196, he still managed to reach base at a .336 clip. His at-bat quality makes him the type of hitter you want near the top. If the Padres aren't moving Luis Arraez out of the top spot (more on that later), there's a Tatis/Profar question.

Would the Padres really drop Machado and Merrill lower?

For the most part, the current lineup is working. As I wrote last week, this is already the best offense in Padres history. They've accomplished that with Jackson Merrill hitting sixth and Manny Machado mostly hitting fourth.

Lately, however, Merrill and Machado have been San Diego's two best hitters. If the Padres stick Tatis near the top and drop everyone else, that means Machado... fifth? And Merrill... seventh? Is that really optimal?

How could the Padres elevate Merrill?

I don't know whether Merrill will win NL Player of the Month. But I know he should. Merrill batted .303/.343/.626 in August with all manner of clutch hits. Sounds like a cleanup-type hitter to me.

That role would otherwise belong to Jake Cronenworth. Make no mistake, Cronenworth takes fantastic at-bats. But if the Padres are optimizing their lineup, putting Merrill fourth against righties makes sense.

Any questions about Merrill's ability to handle the role? You must not have watched Jackson Merrill. Any questions about Cronenworth's willingness to cede at-bats for the good of the team? You must not have watched Jake Cronenworth.

How do you space the three lefty hitters?

The easy answer says 1-4-7. You put two righties between them, and it's a nightmare for opposing managers. I'll counter with a twist: 1-4-6. Cronenworth should still feature as high as possible, because he’s been outstanding against right-handed pitching.

Plus, if he bats sixth, you're setting up an opposing manager to use a lefty to face Merrill-Machado-Cronenworth. That gets you:

1. A Manny Machado at-bat against a lefty
2. The chance to pinch-hit for Cronenworth with lefty-killer Donovan Solano

So what's the lineup then?

Based on all of the above, here's how I could see the Padres lining up vs. RHPs:

1. Arraez, DH
2. Profar, LF
3. Tatis, RF
4. Merrill, CF
5. Machado, 3B
6. Cronenworth, 1B
7. Xander Bogaerts, 2B
8. Ha-Seong Kim, SS
9. Kyle Higashioka, C

Quite a lineup.

And what about lefties?

Three quick considerations:

• Cronenworth hasn't been good against lefties. Solano is. Don't be surprised if Solano starts, with Cronenworth pinch-hitting or replacing Solano on defense.
• Remember how we had Merrill batting fourth? Let's flip him and Machado here, so the lefty-killing Machado hits cleanup.
• I don't think the Padres would do this, because I know they value Arraez's contact/on-base skills at the top. But I see a case for sticking Tatis there against lefties. I can't see many managers keeping a tiring lefty starter in the game against Tatis. And, boom, just like that, you're into the bullpen.

But, like I said, don't see it happening. So here's how the Padres might line up vs. LHPs:

1. Arraez, DH
2. Tatis, RF
3. Profar, LF
4. Machado, 3B
5. Merrill, CF
6. Bogaerts, 2B
7. Solano, 1B
8. Kim, SS
9. Higashioka, C

Where do those lineups leave the Padres’ bench?

In excellent shape. Solano/David Peralta are complementary right/left pinch-hitting options. By signing Elias Díaz, the Padres have a strong defensive backstop they could use in the event they bat for Higashioka.

All the pieces seem to fit. The Padres have spent months hoping they’d have those pieces together for the stretch run. The best-laid plans never unfold smoothly. (And, as things stand, Kim remains sidelined with a shoulder issue.)

Nonetheless, when Tatis returns, the Padres’ potential starting lineups are mouth-watering.