DENVER -- A little rest seems to do wonders for Nolan Arenado.

The Colorado Rockies third baseman has not been in the lineup four times this season and on each occasion the breather has resulted in a productive game.

Never more so than Wednesday when Arenado hit three home runs in a game for the first time in his career as the Rockies walloped the San Diego Padres 18-4, using a 21-hit attack to sweep the three-game series and win their fourth in a row overall.

Arenado had a career-high five hits and tied a personal best with seven RBIs. He also scored four runs.

Arenado's memorable game gave him 21 homers and a major league-leading 80 RBIs this season.

With a shot at a record-tying four homers when he came to bat in the eighth, Arenado ran the count to 3-2 and lined out to left against Kirby Yates.

"I was trying to hit a homer," Arenado said. "That's probably why I didn't. The at-bats before that, I was trying to hit the ball hard and stay on top of the baseball. They went out. On my last at-bat, couldn't help but think about it. He made good pitches. He beat me inside."

In games the day after not being in the lineup, Arenado has gone 14-for-24 (.583) with two doubles, four home runs and 13 RBIs.

"I was more motivated to come play today," Arenado said. "Whenever I have a day off, I'm always ready to play. But I really wanted to play today. I was stretching earlier than I usually do."

Trevor Story and Charlie Blackmon also homered for the Rockies. Story also had three hits, three RBIs and three runs. Blackmon had three hits, two RBIs and three runs.

The Rockies last scored 18 runs on April 27, 2012, and last had 21 hits on Sept. 17, 2014.

The Rockies lost 15 of 20 games from June 21 to July 15, scoring three or fewer runs in 12 of those defeats. But they have emphatically put that dismal offensive stretch behind them, scoring 49 runs in four straight wins while yielding 21.

The Rockies, who lead the majors with 25 wins in day games, scored in each of the first seven innings and strafed Padres starter Clayton Richard (5-10). He allowed career highs in hits (14) and runs (11) while throwing 100 pitches in 3 2/3 innings.

The Rockies hit three homers in their six-run fourth that blew the game open and gave them a 12-0 lead.

Arenado led off the uprising with the first of his three homers. With two outs in the inning, Story belted his 12th home run, a two-run shot that followed Gerardo Parra's broken-bat single.

Gray singled home Ryan Hanigan, who hit a ground-rule double, and Blackmon greeted Kevin Quackenbush by driving his pitch over the fence in center for a two-run shot, his 23rd homer of the season.

"They hit balls through holes, and they blooped balls in and they hit balls off walls and they hit balls out of the ballpark," Padres manager Andy Green said. "Literally, every conceivable type of hit they could get, they had today."

Rockies starter Jon Gray (3-1) pitched six innings. He blanked the Padres for the first five before they scored four in the sixth, three on Cory Spangenberg's seventh homer.

With runners at first and third and no outs in the fourth, Gray sandwiched a Spangenberg pop fly between strikeouts of Jabari Blash and Franchy Cordero.

"I really like the inning where it was first and third and no outs," Rockies manager Bud Black said. "The game at that point was 6-0. They could've crept a little closer and went strikeout, popout, strikeout. I think that was a big confidence boost for Jon, not only today but moving forward."

The Rockies took a 3-0 lead in the first on Arenado's single, a passed ball and Ian Desmond's sacrifice fly.

Arenado's two-out single in the second made it 4-0.

Two more runs in the third put the Rockies ahead 6-0. Story's first triple of the season followed Parra's one-out single, and Story scored when Hanigan singled up the middle with the infield drawn in.

Parra went 4-for-5 and had extended his string of reaching base to 10 consecutive plate appearances before he flied out in the fifth. His string of consecutive games with an RBI ended at eight, but in nine games since being reinstated after a 28-game stay on the disabled list, Parra is 20-for-36 (.556) to raise his average to .364.

NOTES: Rockies CF Charlie Blackmon extended his hitting streak to a season- and career-high-tying 14 games. ... Rockies RHP Chad Bettis (testicular cancer) is scheduled to pitch Sunday for Triple-A Albuquerque and work four innings or 60 pitches in his third rehab start after two with Double-A Hartford. ... Rockies RHP Tyler Chatwood (right calf strain) threw his first bullpen session since getting injured Saturday. ... Padres OF Franchy Cordero was recalled from Triple-A El Paso and RHP Jose Valdez was optioned to that team. ... Padres OF Hunter Renfroe (strained neck) is expected to be activated Thursday when he is eligible to be reinstated. ... Padres OF Travis Jankowski (right foot bone bruise) is scheduled to play nine innings Wednesday and Thursday nights in the Arizona Rookie League and travel Friday to another Padres affiliate to continue his rehab. ... Padres RHP Jarred Cosart earlier this week underwent season-ending arthroscopic surgery on his right elbow. ... Rockies OF David Dahl was reinstated from his minor league rehab assignment and optioned to Triple-A Albuquerque.