Last week it was reported San Diego Padres general manager A.J. Preller was still looking to upgrade the team's roster, specifically at the shortstop position. There are a number of shortstops on the market that could be made available in a trade, including Ian Desmond of the Washington Nationals.

Preller has revamped the Padres in his first season as GM and his willingness to make trades is apparently still unwavering. The MLB's most active team during the offseason is still not done upgrading.

"According to multiple GMs, Preller's aggressiveness has not slowed down since the season began, with an upgrade at shortstop being at the top of his list," writes ESPN's Jim Bowden. "Although he likes both Alexi Amarista and Clint Barmes, his present shortstops, he likes them better as utility players and would prefer a better two-way player who could bring more offense to the Padres' lineup."

Initially it was proposed Preller could go after Starlin Castro of the Chicago Cubs, but Theo Epstein's plan regarding the team's surplus of middle infielders is unclear. Epstein mentioned last week 'big trades' could be coming, but he also noted all of the players in question - Castro, Arismendy Alcantara and prospects Addison Russell and Javier Baez - are capable of playing together in the field because of their defensive versatility. Additionally, Patrick Mooney of CSN Chicago said it might not be the best idea to trade Castro just yet because he's finally on a solid Cubs team with managerial stability.

Colorado Rockies star Troy Tulowitzki is another option, but general manager Jeff Bridich would likely want a favorable package deal that is heavily concentrated on pitching for the All-Star, that is, if the team isn't contending, which they believe they can do as long as Tulo and outfielder Carlos Gonzalez are healthy.

"Naturally, the Padres would love to swing a deal for Troy Tulowitzki, but all indications are that the Rockies believe they'll contend and aren't motivated to move him. Even if that changes, Colorado is unlikely to deal him to a team in the same division," adds Bowden.

Also, it's unknown if San Diego would be willing to inherit such a costly contract.

This leaves Desmond as a likely option, considering the Nationals have yet to enter contract talks with the 29-year-old after he rejected a $107 million offer prior to the 2014 season. Nats GM Mike Rizzo said prior to the season that the team would be open to trading Desmond if it made "baseball sense," further indicating they're ready to move on from the shortstop.

The Padres and Nationals were involved in a three-way trade earlier this offseason and Washington received shortstop Trea Turner (they'll officially get him in June) from San Diego in a move that could line up the prospect as Desmond's successor within the next few seasons (since they have shortstop Yunel Escobar under contract through 2016).

"Desmond will be a free agent at season's end, and all indications are this will be his last year in Washington. He's one of the best offensive shortstops in the game, and his 20-homer, 20-steal ability would be a huge boost to the Padres' offense. It's unlikely the Nationals trade him, but with Preller and Nats GM Mike Rizzo, anything is possible," Bowden writes.

Perhaps Washington wants to get Desmond off their hands to obtain value for him before he hits free agency. The Nats are hoping to contend for a World Series title with the current roster they have, and Desmond is an integral part of the team as long as he's producing like he usually does, but he's off to an inauspicious start thus far. On top of committing five errors in the first seven games, the three-time Silver Slugger is batting just .115/.179/.192 with two runs scored and one RBI in 28 plate appearances.

It's hard to believe the Nationals are going to let both Desmond and starter Jordan Zimmermann walk at the end of the season, so keep an eye out for Desmond's name to be mentioned in trade rumors as the season progresses.