"Obviously, we played sloppy," said third baseman Ryan Zimmerman, who made one of the miscues and smacked two of the homers. "We need to clean that up."
The mistakes also made Ross Detwiler's day on the mound more arduous than it needed to be. Detwiler (0-2) allowed seven Arizona runs (four earned) on nine hits in four-plus innings.
First baseman Adam Dunn's fielding flub in the second on Rusty Ryal's softly hit grounder to first base allowed Adam LaRoche to score from second, and Ryal scored a batter later on Bobby Crosby's double down the right-field line.
The other corner infield spot also wasn't kind to the Nats in the fourth. Zimmerman's 11th error of the season allowed Crosby to reach and Ryal to advance to second before Stephen Drew and D-backs starter Barry Enright each collected RBI singles to make it a 4-1 game.
"If I get another ground ball right after an error," Detwiler said, asking for his share of the blame, "then we can get out of the inning. I was just giving up hits after errors, which hurts us even more."
But young Detwiler can't dispute this: Washington's 86 errors through 109 games are the most in the Major Leagues.
"It's a ballgame; I don't want to say the sky is falling," cautioned manager Jim Riggleman of his club (48-61), which has still won six of 10. "We played bad defense for about six weeks straight back in middle of May until late June, and then we started playing good. Too many nights like that put us where we are in the standings, and we were making a lot of progress, but we took a step backwards tonight."
And not even four baseballs clearing the outfield fence made a difference. Zimmerman going to right field off Enright in the fifth and to left against reliever Esmerling Vasquez in the eighth only made a dent.
"Zimmerman, he's a beast," D-backs interim skipper Kirk Gibson said. "You look at those guys, they're pretty darn good hitters so I'm going to give those guys some credit."
Counting Zimmerman's pair of long balls, Adam Kennedy's in the third and Roger Bernadina's in the seventh on Thursday, however, Washington hit 10 dingers in the four-game series, and all but one were of the solo variety.
And Detwiler -- putting aside his teammates' blunders -- could have used a three-run shot. After all, 11 of the 22 batters he faced reached safely, including three straight hits before he was lifted with no outs in the D-backs' three-run fifth.
Detwiler faulted himself for the D-backs hit parade, noting that he left his fastball up in the zone. He indicated that he and pitching coach Steve McCatty would look at the video of his start to determine if any mechanical changes are needed.
The Nats had early opportunities to ease Detwiler's way into Thursday's game, opposing the rookie Enright (3-2), who was selected 67 spots behind sixth-overall pick Detwiler in the 2007 First-Year Player Draft.
They didn't capitalize.
For example, after Ian Desmond's second-inning double, Washington had runners at second and third base with one out, but Desmond was forced out on Wil Nieve's comebacker to the mound and Detwiler struck out on three fastballs.
The Nats were seeking their third straight series victory and their first road series win since May 10-12 at the Mets. Both achievements will have to wait.