CHICAGO -- Cubs relievers boasted the second-best ERA and had the fewest losses in the National League entering Sunday, but president of baseball operations Theo Epstein says they're on the lookout to add an arm before the July 31 non-waiver Trade Deadline.
"You're always looking to upgrade this time of year when you have a competitive team," Epstein said Sunday. "No matter how well your 'pen has pitched, there's always a desire to look around and see if you can tweak it and improve it. You're always cognizant of the fact that you can address it after July 31."
The Cubs have been linked to Orioles reliever Zach Britton, who could give them another closer option. Brandon Morrow is currently on the disabled list with right biceps inflammation, and Epstein said that injury isn't influencing what moves they may make. The Cubs did pick up an extra arm on Thursday in right-hander Jesse Chavez, who is a versatile pitcher and a "real stabilizer," Epstein said.

The Cubs have been using young relievers such as Dillon Maples, Justin Hancock, Luke Farrell and Randy Rosario in key roles this season. Manager Joe Maddon wouldn't mind having a more experienced pitcher to call upon as well.
"You have young guys in the bullpen you think are going to be really good, but when it gets to that high-leverage moment in the latter part of the game, it's tough to just call their name before you've had the chance to break them into that moment," Maddon said. "Sometimes you're forced to do it."
Britton, 30, was sidelined at the start of the season until mid-June because of a ruptured right Achilles tendon. He has not given up an earned run in his past eight outings, and he has walked 10 while striking out 13 over 15 2/3 innings overall.

Chicago reliever Pedro Strop knows Britton from their days together with the Orioles.
"If you can add a guy like that to the bullpen, I'm not going to say you don't need it," Strop said. "You're talking about one of the best closers in the game.
"We're good," Strop said of the Cubs relievers, "but if you can add him, our bullpen could be so deep."
The Cubs entered Sunday with the best record in the NL, yet they still need reinforcements.
"Pitching is the main need," Epstein said. "The end of August, we might be looking for somebody who can play defense or steal a bag. I'm not saying we have a perfect position-player group, but [prospect] David Bote is a really good player and we can't find a spot for him now. There are intriguing guys out there who you'd love to have, but roster space and playing time are realities you can't get around."
Worth noting
• Yu Darvish played catch from 135 feet on Sunday, and the next step will be to throw off the mound, Epstein said.
"Today was his best day in a long time, and he threw really well and felt really good," Epstein said of Darvish, who has been out since May 23 with right triceps tendinitis.
Drew Smyly, who is rehabbing from Tommy John surgery last year, threw a simulated game at Wrigley Field and will do so again on Thursday. If all goes well, the next step for the left-hander would be a rehab assignment. Smyly will be stretched out in the Minors so that he'll be a possible spot starter later this season.
"It'll be good for him to get the reps in and get his feel back and lock in his mechanics and test his arm," Epstein said. "It also allows for some versatility when he is ready to come back. He could start or go right to the 'pen and be in more of a hybrid role."
• Infielder Thomas La Stella was one of the three Cubs position players who pitched in relief on Friday. It was the first time he did so since his sophomore year in high school.

"As soon as I realized I was going to be able to throw it over the plate, I was relieved," La Stella said on Sunday. "It had been awhile since I busted it out. It felt good -- it was very nostalgic for me."
La Stella, catcher Victor Caratini and outfielder Ian Happ all pitched in, combining for 3 1/3 innings.
"At that time, it's all about saving the bullpen," La Stella said.