San Diego Padres' general manager A.J. Preller is seemingly confident the team can still make a run at the postseason, even in the competitive NL West where the Dodgers and Giants headline the show. Well, if that plan backfires, Preller could look to make some waiver trades involving the team's top players.

The Pads made one deal before the July 31 non-waiver deadline and did not move one of their players. San Diego (51-54) has won seven of their last 10, but they are nine games behind the Dodgers for the lead in the division and 6.5 games behind the Chicago Cubs for the second NL wild-card spot. A big run in August or September is certainly not out of the question, but this Padres team could still be subject to trade rumors if they can't make up some ground in the next few weeks.

Starting pitcher James Shields has already been mentioned as a waiver-trade candidate and now outfielder Justin Upton could enter those discussions.

"Shields is a guy the Padres might be able to slip through waivers because of his hefty salary," writes Nick Cafardo of the Boston Globe. "It's hard to imagine a team putting a claim in, so Shields could be an August acquisition for a team such as the Yankees, who didn't solve any pitching needs ...

"Upton again could be a waiver deal if the Padres feel they're out of it at some point. The Padres shocked baseball by not trading anyone, but at a minimum teams seeking hitters thought Upton would go."

ESPN Insider Buster Olney weighed in on Shields' potential trade status before the deadline.

"Some rival evaluators believe the trade deadline won't really apply to James Shields, because of the $60-plus million owed to him over the next three seasons. Rather, the expectation is that Shields would clear waivers in August, presenting the Padres more time and opportunity to trade him before the offseason begins."

As for Upton, a lot of contenders may consider claiming him if they're in need of a bat.

Here are the basics about MLB waiver trades:

The player in question must pass through "revocable waivers" before he can be traded without restriction

Revocable waivers last 47 hours and if the player is not claimed by another team he can be traded anywhere, released or pull of revocable waivers by his team

If the player is claimed by another club, the two teams have 48.5 hours to work out a deal before the player returns to his incumbent team

A trade must be made by August 31 or else players acquired after that date cannot play in the postseason

San Diego will likely be the club at the forefront of the rumors discussion regarding waiver deals.

While there are various reasons (check out this piece by ESPN's Jayson Stark) as to why many believe the Padres didn't sell before the deadline, the reality of doing so may hit Preller as the month of August progresses. While it's been said San Diego is willing to take the draft pick compensation in return for Upton (when he declines the qualifying offer), that would not be maximizing the outfielder's value. He's expected to be the most coveted free-agent bat in the offseason and to only get a first-round draft pick for him is no justice considering what he'll provide for another club in the long-term.

The Tigers (David Price, Yoenis Cespedes), Cincinnati Reds (Johnny Cueto, Mike Leake) and Oakland Athletics (Scott Kazmir, Ben Zobrist) got good, if not great, value in return for their impending free-agent players. Was that not enough of a blueprint for Preller to replicate?

Whatever the case, the second wild-card spot has created fervent competition in the MLB and now discussions about moving the trade deadline back have already taken place. Teams such as the Tigers and Blue Jays epitomized this deadline conundrum where general managers are scrambling to decide if they are going to buy or sell.

At the day of the deadline, the Tigers were 3.5 games out of a wild-card spot and the Blue Jays were one game out. Not a big difference at all, especially in the wide-open American League. However, the Tigers went on to sell their top players at the last minute while the Blue Jays made enormous acquisitions including Price, Troy Tulowitzki, Ben Revere, LaTroy Hawkins and Mark Lowe.

Preller wasn't in one of those predicaments. Even the basic statistics imply the Padres are not a contender and their issues will not be solved overnight. The club ranks 21st in the MLB with 408 runs scored, 19th in defensive runs saved (-5) and 16th in team ERA (3.89), while their middle infield still remains a big question mark.

Perhaps Preller saw an opportunity immediately after the deadline: his team faces the Miami Marlins, Milwaukee Brewers, Cincinnati Reds, Philadelphia Phillies, Colorado Rockies and Atlanta Braves in consecutive series. However, if they can't capitalize in those matchups before they face the St. Louis Cardinals and Washington Nationals at the end of the month, don't be surprised if Shields and Upton are gone on or before August 31.