Once upon a time Starlin Castro was a valuable trade chip for the Chicago Cubs. At the beginning of the season trade rumors suggested the shortstop could yield a decent return, but at this point in July it appears as if that's a faint memory.

Castro is batting .240/.273/.309 with 29 runs scored, 5 home runs and 39 RBIs in 91 games this season in what could be the worst offensive stretch of his career besides his 2013 campaign. On top of that, his defense has been poor for much of the year.

He has 15 errors thus far, and according to advanced metrics from FanGraphs, Castro is 18th in the MLB with -3 defensive runs saved. However, the 25-year-old has never been known for his glove. His solid all-around offensive production is what bailed him out. But now the Cubs don't even have that to sell.

"I think that the Cubs came into the year thinking that perhaps an opportunity would develop for them to consider a trade of Castro in midseason, because let's face it, in two or three years Addison Russell will be there everyday shortstop," ESPN Insider Buster Olney said on the Baseball Tonight Podcast. "But he has not played well, he's owed a lot of money and it'd be a really difficult time to trade him. I think this is going to be a more complicated trade that's going to take place during the offseason."

He's still young and has a lot of time left in the MLB, but there aren't many clubs willing to take on a defensive liability at about $41.5 million from 2016-2019. That hasn't stopped the Cubs from involving him in trade discussions.

"Other clubs say the Cubs are dangling Javier Baez and Starlin Castro as the centerpieces of a potential deal. But the Phillies appear no more than lukewarm about either of them," writes ESPN's Jayson Stark.

The reality of it is that Chicago might need to start considering a position change for Castro. Rumors previously suggested third baseman Kris Bryant could move to the outfield, which would open up a spot for Castro at the hot corner and allow Russell to move to shortstop. Second base could be an option too, but his range and awareness have proven to be an issue in the middle infield. Baez could take over there soon anyway.

But there is another option to consider.

Last week we talked about a potential Castro-for-James Shields trade with the San Diego Padres. This could be beneficial for both clubs for many reasons. Scouts have said Castro needs a change of scenery; he would be an upgrade for San Diego's awful middle infield; the Cubs need starting pitching and Shields would provide stability atop the rotation; and the Padres would save nearly $25 million (and a lot more money on a per season basis) by switching Shields' contract with Castro's.

The Padres have already talked to teams about moving Shields and it's very possible the Cubs were one of them. The right-hander was considering Chicago before taking a $75 million deal from San Diego. However, Padres' general manager A.J. Preller is looking to replenish the assets he lost making numerous trades in the offseason and he may not consider Castro to be a good return for Shields.

Especially if many other teams don't view him as such.

"I spoke to multiple MLB execs/scouts today," David Kaplan of CSN Chicago said on Twitter. "Common theme: Starlin Castro has little trade value right now. Can't be centerpiece of big deal."

The trade deadline is less than nine days away, so we'll see if Theo Epstein and Jed Hoyer have any tricks up their sleeve to move Castro.