DENVER -- The Giants start their six-game road trip through Colorado and Arizona with a reinforced bullpen, boasting five new arms added over the past 10 days.

The Giants added right-handers Jean Machion and Brad Penny on Sept. 1, Dan Otero on Tuesday and Yusmeiro Petit on Friday, and they added lefty Dan Runzler on Tuesday. Otero and Penny have pitched in nine and 17 big league games this season, respectively, but Machi, Runzler and Petit have only thrown a combined 2 1/3 innings in 2012.

"Those guys are probably going to be in the game, some of them that haven't pitched in a little while," manager Bruce Bochy said before Monday's series opener with the Rockies. "We're going to need them to do well, pitch well, do their job."

Coors Field is notorious for taxing bullpens, and Arizona can run through its share of relievers as well. With the Giants entering Monday with a 5 1/2-game lead in the National League West, the reinforced bullpen brigade should help keep the club fresh down the stretch.

"You can't keep going to the same guys," Bochy said. "You're getting toward the end of the season, but these guys still need a break."

The 'pen is having its best month since April, posting a 2.79 ERA and a 3-2 record while saving three of four opportunities.

"They're all doing well," Bochy said. "One guy I'll check with is [Santiago] Casilla. His outings have been short until yesterday. I think he threw 16 pitches. I'll see how he's doing."

Hensley should return to bullpen Tuesday

DENVER -- The Giants are set to get a key cog from their bullpen back in action starting Tuesday.

Right-handed reliever Clay Hensley has been on the disabled list with a right groin strain since Aug. 27. He last pitched against Atlanta on Aug. 26, and went to the DL to make room for Jeremy Affeldt. He's eligible to come off Tuesday, and manger Bruce Bochy said he's on track to be activated.

"He's going to take a bullpen today during BP, so he's set to come off," Bochy said before Monday's series opener with the Rockies. "He feels good."

Hensley has been a workhorse in the 'pen, throwing in 54 games and posting a 4.37 ERA and a 4-3 record. He's been part of the Giants' "closer by committee" corps and has saved three games while finishing 14 this season.

Nady close to returning to action

DENVER -- Outfielder Xavier Nady remains on track to return to action soon, but as he nurses a left hamstring strain, the spacious Coors Field outfield may not be the best place to test the newly minted Giant in the field.

"He ran [today]," manager Bruce Bochy said before Monday's first game in a three-game set with the Rockies. "[Head athletic trainer Bill] Groeschner put him at about 60 percent. He's going to let me know if he's available to pinch-hit, and possibly he could be ready to play in the Arizona series."

Nady signed a Minor League contract with the Giants on Aug. 5 after Washington designed him for assignment. He hit .157 (16-for-102) with three home runs and six RBIs in 40 games with the Nationals, and hit .270 (24-for-89) with six homers and 18 RBIs in 25 games with Triple-A Fresno. After a Sept. 1 callup, Nady went 4-for-13 with the Giants before getting hurt in the seventh inning of Wednesday's game against Arizona.

"He's coming along quite well," Bochy said. "It's encouraging to see how he's doing. He'll be doing some stuff, taking batting practice."

If he recovers well, Bochy plans to use Nady as part of a left-field platoon with Gregor Blanco, with Nady getting the call when a lefty toes the rubber.

"Good chance [he'll play left against lefties], yeah," Bochy said. "I'll see where he's at. If he's not 100 percent or close to it, it's hard to put him out in left field."