OAKLAND -- Since the A’s began their three-year run of consecutive postseason appearances in 2018, they’ve continuously grown in talent to challenge the Astros’ perennial dominance of the American League West by slowly closing the gap each season. The culmination of that pursuit came last year, when the A’s dethroned Houston and captured their first AL West title since 2013.

So far in 2021, the disparity between the two clubs is feeling an awful lot like it did prior to Oakland’s emergence as a serious contender three years ago.

A one-sided series from start to finish ended with the A’s dropping their fourth game in a row against the Astros with Sunday’s 9-2 loss, which completed a four-game sweep for Houston. The A’s never led at any point in the 36 innings played over the series, marking the first time they’ve never led in such a series since July 19-22, 2017, which also came against the Astros at the Coliseum.

“It’s a little bit embarrassing,” A’s manager Bob Melvin said. “We played really poorly and they played great. In perspective, we have to look at it as just four games in 162. But we obviously have to play better.”

The positives for the A’s were scarce in a series in which they were outscored 35-9 and out-homered 8-1. The closest margin of defeat was four runs on Friday night. The other three losses: seven, seven and eight. In Melvin's words, this series was “ugly.”

The A’s are now 0-4 to start the season for just the third time since the club moved from Kansas City to Oakland in 1968. They lost their first five games of the 1979 and ‘87 season before winning the sixth game. They did not reach the postseason in either year.

There are a few things that can be attributed to Oakland’s slow start. They’re dealing with injuries -- Ramón Laureano and Sean Murphy missed Sunday’s game as they deal with hand injuries and Chad Pinder left the game in the first inning with a sprained left knee after crashing into the right field wall making a catch.

The clutch hits are missing: Oakland went 4-for-28 with runners in scoring position in the series and stranded 25 runners on base. Several top hitters are slumping, including third baseman Matt Chapman, who is batting .091 with just one hit in four games.

The bullpen, which led the Major Leagues with a 2.72 ERA in 2020 and was expected to again be a team strength in 2021, is getting hit around through four games. New closer Trevor Rosenthal began the season on the injured list, which was a tough blow. But the eight-man relief corps combined to allow 16 runs in 16 2/3 innings against Houston.

On Sunday, Sean Manaea departed with the A’s still within striking distance after allowing five runs in 4 2/3 innings. With the A’s trailing 5-2 after five innings, the Astros quickly broke it open in the sixth with four runs, including a three-run homer by Chas McCormick off Yusmeiro Petit. Petit entered the game in relief of Adam Kolarek, who was charged with the majority of those runs on the homer after allowing two hits and lasting just two-thirds of an inning.

“Especially against a division rival like these guys, it’s a tough way to start the season,” Manaea said. “I don’t think anybody is happy with how we’ve played. It’s tough. But we’ve just gotta keep going.”

With such high bullpen usage in the series, Melvin said the club could make a call down to the club’s alternate training site in Stockton to add fresh arms.

“We’ll probably talk about that,” Melvin said. “I don’t know yet.”

The schedule won’t be letting up for the A’s anytime soon. They’ll welcome the defending World Series champion Dodgers to town for three games beginning on Monday before traveling to Houston for a three-game series next weekend. The first month of the season does not determine a team’s fate, but the A’s are certainly approaching an undesirable situation in a year where they envisioned not only a successful defense of their AL West title, but also a deep playoff run.

“We’ve got another tough team coming in and then we go to Houston,” Melvin said. “We gotta turn things around. It’s not just going to happen for us. We have to play better baseball, and this was not good baseball for us.”