SAN DIEGO -- The year was 2016, and the Padres, suffice it to say, were in a very different phase of their roster construction.

The primary goal then was acquiring young talent, by any means possible.

The Padres entered camp that year with four Rule 5 Draft picks, two of whom cracked the Opening Day roster. Later that summer, ownership made an unprecedented investment in the international market, spending north of $80 million on prospects (a shrewd move in what would become the final uncapped international spending year). That December, when the Rule 5 Draft came along again, the Padres acquired three more prospects.

• These prospects face roster/Rule 5 decision | Padres' Top 30 Prospects

This is particularly relevant now because the Padres find themselves on the opposite end of that spectrum, trying to cling to as much of their talent as possible.

It’s time to pay the piper for that talented 2016-17 international class, and that payment might come in a familiar form: the Rule 5 Draft.

An important roster deadline looms for the Padres on Friday. Here's what you need to know:

What happens Friday?
Friday marks the deadline for teams to add players to their 40-man roster, thus protecting them from the Rule 5 Draft. (Rule 5 eligible players include those with five pro seasons who signed at age 18 or younger or four pro seasons who signed at 19 or older.)

Any players left unprotected will be eligible to be selected by another team. Those players must remain on the Major League roster for the duration of the 2021 season or be offered back to the Padres.

In short: The bulk of that 2016-17 international class is now Rule 5 eligible (if they aren’t already on the 40-man roster). The Padres need to figure out which eligible prospects they want to protect.

Whom will they protect?
General manager A.J. Preller began working ahead at the Trade Deadline when he shipped eligible prospects Taylor Trammell, Gabriel Arias, Jeisson Rosario and Hudson Potts.

But he still has quite a group players eligible for the Rule 5 Draft. From MLB Pipeline's ranking of the Padres' Top 30 prospects, here is the list, in order of the prospect's ranking:

8. Tucupita Marcano, INF
9. Reggie Lawson, RHP
10. Tirso Ornelas, OF
11. Esteury Ruiz, 2B
12. Lake Bachar, RHP
13. Pedro Avila, RHP
14. Eguy Rosario, INF
15. Jordy Barley, SS

From that group, Marcano -- a 2016 international signing -- is a lock to be added. Lawson probably is, too. He had Tommy John surgery in March and could easily be stashed on the injured list by an opposing team for a sizeable chunk of the 2021 season.

After that, the team's plans are unclear. There's plenty of talent, but the Padres also have built a talented big league roster, and 40-man spots are precious.

What are the roster implications of protecting players?
The Padres' 40-man roster is at 38 players, leaving space to add Marcano and Lawson.

After those two, there are decisions to make. Ornelas hasn't quite made the strides the Padres had hoped for. But he's still only 20 with serious upside. Avila spent 2020 recovering from Tommy John surgery. He might provide decent depth for a rotation that might need it.

If the Padres decide to add anyone beyond Marcano and Lawson, it would come at the expense of a player or two already on their 40-man roster. The likeliest non-tender candidates this offseason are right-handers Luis Perdomo and Javy Guerra and infielder Greg Garcia.

Could the Padres make a trade?
Absolutely. If they want to free up space on their 40-man roster, a trade is the best way to do so while getting something in return.

Two years ago, Preller made a flurry of moves on Rule 5 Deadline day. None were earth-shattering, but all sent eligible players to other teams in exchange for either cash or other Minor Leaguers who weren't yet Rule 5 eligible.

As things stand, the Padres have 24 pitchers on their 40-man roster, a number of whom don’t factor seriously into the bullpen mix next year. It's easy to envision another team paying a small price for a relief option like David Bednar or Taylor Williams.

Prediction
Expect the Padres to add Marcano and Lawson. Marcano projects as a big league-caliber middle infielder. Lawson has upside and could factor into the team's future rotation mix.

That puts the roster at 40. Perdomo, who underwent Tommy John surgery last month, is the likeliest candidate to give way. But the guess is that Preller looks to trade a fringe bullpen arm, freeing up room to add Ornelas (or a more polished rotation arm like Avila or Bachar).

That might simply delay the inevitable for Perdomo and his ilk. The Padres will need to clear roster space in the future if they add a free agent. The deadline to tender 2021 contracts to players is Dec. 2.