Rockies right-hander Germán Márquez gave up a first-inning, two-run homer to the Mariners' Dylan Moore, and the offense -- outside of Charlie Blackmon's double and single to extend his hit streak to 13 games -- struggled until the late stages of a 5-3 loss at T-Mobile Park.

Sunday’s loss prevented Colorado from a three-game sweep in Seattle, but the Rockies still have won their first five series this season and are in first place in the National League West, at 11-4. Colorado will embark on a stretch of eight of its next 10 games at Coors Field, with a three-game series against the D-backs starting Monday. 

• Box score

Here are five areas of note coming into the upcoming stretch:

1) No one is getting Blackmon out
Blackmon had two hits against Mariners lefty Justus Sheffield, who held the Rockies to four hits in six scoreless innings. Not only is Blackmon 27-for-51 during the run, but within that, he’s an insane 14-for-21 with three doubles and a homer against lefties. The D-backs will start lefty Robbie Ray on Monday.

2) Will Nolan get right?
The Rockies on Sunday sat star third baseman Nolan Arenado, who is hitless in his past 14 at-bats. Arenado spent much of the pregame on Sunday working with Rockies hitting coach Dave Magadan and assistant hitting coach Jeff Salazar.

“He cares a lot about obviously this organization and his performance,” Black said. “And at times he can beat himself up. But I think I'd rather have, you know, a player that way than the other. He'll come out of it, as we know.”

There is some light in the numbers: Arenado's strikeout rate sits at a minuscule 6.6%, he hasn't struck out since last Sunday and he is hitting .341 (14-for-41) with three home runs, five doubles and a triple against Ray.

3) This success is sustainable, as long as starting pitching holds
Márquez did not exhibit his normal sharpness -- he allowed three leadoff men to reach after allowing just one in his previous two starts. Márquez pulled together after the first, and was hindered in the seventh when Chris Owings, playing third, committed two errors on the same play in the Mariners' three-run inning. Márquez could have limited the damage, but he gave up a couple two-out singles, including one on a hanging breaking ball to Tim Lopes.

“Innings 2-6, in a way, he sort of breezed through it," Rockies manager Bud Black said. "They dumped in a single, but overall, there weren’t a lot of hard-hit balls against Germán.”

Still, just two of the five runs against Márquez were earned, so no Rockies starter has given up more than three earned runs in the past 21 games dating to last season.

“As starters, the best thing we can do is keep the game close and battle with the best stuff you have,” Márquez said.

4) For all the success...
Arenado is far from the only key Rockies player struggling. David Dahl (.246, .606 OPS) and Ryan McMahon (.200, 22 strikeouts in 50 at-bats) were placed lower in the lineup for the final two games of the series. Trevor Story is also stumbling since his strong start, going 8-for-his-last-35.

“We do have a few guys who are scuffling, not to their career norms or swinging the bat like they’re capable,” Black said. “Hopefully, it's just a matter of time before they turn around. Hopefully it happens quick. We’ve talked about the shortened season many times.

“It's gonna happen, you know. We've seen good things from most of our guys over their careers. Even though some of the guys have had shorter careers, there's enough of a sample to think that things are going to turn.”

While Matt Kemp has grabbed the everyday designated hitter job -- expected, given his track record -- Sam Hilliard and Raimel Tapia will have to find their swings with fewer opportunities.

5) Opposing bullpens are the key to happiness
The Rockies’ brief bit of offensive life came in the three-run eighth, with all the scoring with two outs. In the series, the Rockies scored 12 of their 16 runs off relief pitchers, continuing a season-long trend that was especially evident during their last homestand.