McCarthy, the starter in Monday's home opener against San Francisco, allowed three runs on six hits in six innings. Smardzija, the Cubs' opening-day starter Monday at Pittsburgh, went three innings, giving up a run on four hits.
The Diamondbacks amassed 20 hits, including six home runs. Mark Trumbo and Chris Owings were among the Arizona players who homered.
The Diamondbacks played for the first time since returning Sunday from Australia, where they opened the regular season with a pair of losses to the Los Angeles Dodgers.
Manager Kirk Gibson wasn't in the Arizona dugout after undergoing surgery to repair a torn meniscus in his left knee. Bench coach Alan Trammell took Gibson's spot.
Gibson hobbled in on crutches for his pre-game news conference and said he expected to be back in the dugout for the Diamondbacks' split-squad game against Cleveland on Thursday. It will be the final game for Arizona at its Scottsdale spring training facility.
Although it didn't count, the blowout felt good for the Diamondbacks after two disappointing outings in Australia.
''This is what the doctor ordered right here, I mean it really was,'' Trammell said. ''The fact is that we are a good hitting ball club and we need to sustain rallies and do these things, and that was very encouraging.''
The Cubs play their final game of spring training at their new Mesa digs Thursday against the crosstown rival White Sox.
The Diamondbacks and Cubs play exhibition games Friday and Saturday at Chase Field in Phoenix.
Cubs: Samadzija struck out two with no walks. He finished the spring with a 5.14 ERA but said he was ready for the season to begin.
''The last two times out have been really positive,'' he said. ''You kind of look at all fronts - arm strength, body strength, mechanics, location of pitches. And I'm checking off all the boxes, so I felt good and I'm ready to get going.''
Diamondbacks: McCarthy's spring was the best of any Arizona starter. He finished 2-0 with a 2.70 ERA. On Wednesday, he struck out six with one walk.
''Whether it's a minor league or big league game, I felt like I threw most of the pitches where I wanted to,'' he said of his spring efforts. ''I threw with conviction. The stuff was all there. I was able to accomplish what I wanted to while I was here. Those were all good things. How those translate into the regular season we'll find out, but I feel like I'm in a real good place.''
Cubs: OF Justin Ruggiano was a late scratch and was given a second day to rest his sore left ankle. Ruggiano, acquired in an offseason trade from Miami, is hitting .297 with two home runs this spring.
Diamondbacks: OF Cody Ross, recovering from a severe hip injury and subsequent surgery, remains ahead of schedule in his recovery. Gibson said Ross looks good at the plate and the only thing he is waiting to see is how Ross maneuvers in the outfield in game situations. Ross could be back the second week of the season. RHP Bronson Arroyo is coming back from a sore back. Arroyo is scheduled to start Saturday's exhibition game and could be in the rotation for either the fourth game of next week's Giants series or April 4 in the series opener at Colorado.
There's been no announcement as to who will win the Diamondbacks' starting shortstop job, but Owings provided another glimpse of his hitting ability with his two-run homer after replacing Didi Gregorius in the sixth.
Owings, the PCL player of the year last season, is hitting .298 this spring. Gregorius, a superior defender but weaker at the plate, is batting .195.
HOME RUN ALLEY
Cubs left-hander Chris Russin had a rough day, allowing nine runs on 10 hits, including four homers, in 2 2-3 innings.
He gave up a two-run shot to Trumbo in the fourth, then gave up three home runs in Arizona's six-run sixth.
Russin was one of three players acquired from Texas in the July, 2013, trade that sent Matt Garza to the Rangers.