"I don't think this is a ball club that really needs a wake-up call. We just need some guys to perform a little bit better than they did in the first half. They just got off to some slow starts," Towers said,.

"Makeup-wise, chemistry-wise, I feel very strongly about the guys we have in that clubhouse. Probably this year more so than some of my prior years here, I don't know how much I really don't want to mess with that. Over the long run, I think these guys will persevere and end up hopefully on top of this division."

Towers does not have to look far for available left-handed specialists. Among the possibilities:

-- Joe Thatcher. The Padres are expected to be sellers after falling nine games off the NL West lead, and Thatcher is a familiar face. While in San Diego, Towers acquired Thatcher from Milwaukee in 2007. Thatcher, 3-1 with a 2.15 ERA this season, is holding left-handers to a .190 batting average. He has one year of arbitration eligibility remaining.

-- Javier Lopez, who was drafted by the D-backs in 1998, is among the players the Giants are said to be willing to trade. He is among the best situational lefties in the game, and San Francisco has won two of the last three World Series since acquiring him at the 2010 trade deadline from Pittsburgh. Lopez, 1-1 with a 1.42 ERA, has permitted only five of his 39 inherited runners to score. He is owed about $1.4 million for the rest of the season and will be a free agent at the end of the year. The Giants got him for Joe Bowker and Joe Martinez, but the cost might be higher this time. San Francisco would consider re-signing him over the winter, although indications are that Lopez would like to play closer to his Virginia home.

-- The Cubs' James Russell, who has held lefties to a .179 batting average this season, retired three of the five left-handed-batting D-backs he faced earlier this week, walking the other two. He has six failed conversions this season, although all of those have come as a setup man; he has not been used as a closer. Russell is due about $380,000 for the rest of the season and has two years of arbitration eligibility remaining.

-- Mike Gonzalez (Milwaukee), Oliver Perez (Seattle), Mike Dunn (Miami) and Charlie Furbush (Seattle) also appear to be available.

Because of Randall Delgado's strong work since joining the rotation in June, the D-backs have an extra starter, a situation they will need to address when Trevor Cahill is activated from the disabled list. Cahill is to make a rebab start for Class AAA Reno on Tuesday, and he might need one more before the D-backs bring him back. It is a good problem to have, and it does give the D-backs some bargaining chips.

Ian Kennedy has been mentioned as a trade candidate amid a disappointing season. His 5.22 ERA is third-highest among NL qualifiers, so his value is down, but he did win 36 games over the previous two years.

Their outfield depth also could be leveraged to fill the bullpen need for a left-hander. The D-backs simply cannot find enough playing time for their five outfielders: Adam Eaton, Jason Kubel, Gerardo Parra, A.J. Pollock and Cody Ross. Martin Prado also has played left field.

Towers made it a point to say no one is untouchable, but trading partners would have to dig deep to pry away top prospects such as Archie Bradley, Skaggs, Chris Owings or Matt Davidson. Major league scouts have been following Reno recently, one scout said, perhaps to get a better read on Davidson and Owings.

"If we are going to move one of our top guys -- not that there are any guarantees -- the particular player we would be getting back, we would have to really feel is going to make a huge difference in the division" race," Towers said.


Follow Jack Magruder on Twitter