The Hammers just about scraped through on penalties after drawing 1-1 with Maltese minnows Birkirkara in the last round.
But those struggles looked a distant memory as they dominated FC Astra for the opening hour going 2-0 up and star man Dimitri Payet shining on his competitive debut.
It all went wrong, though, as the visitors scored two precious away goals following James Collins' sending off. It was undoubtedly West Ham's toughest test in the competition so far, but what did we learn from the match?
1) West Ham are making a mockery of the soon to be defunct Fair Play League
West Ham were the first Premier League side to be back in competitive action after qualifying for Europe through the FIFA Fair Play rankings. But they have set about making a bit of a mockery of that route into the competition having had a player sent off in each of the three rounds so far as well as seeing manager Slaven Bilic sent to the stands.
From this season on teams will no longer qualify for Europe through the Fair Play Table and will instead receive one-off cash rewards, not that the Hammers would have much hope of repeating the feat if their pre-season discipline is anything to go by. Yes there have been some harsh decisions amongst those but Bilic made his side aware of what to expect and in each round they have suffered avoidable dismissals.
2) James Collins should practice what he preaches
Ahead of the first leg against Astra, James Collins appeared alongside his manager Bilic for the pre-match press conference. The experience Wales international sent a rallying cry to his West Ham team-mates to be more 'streetwise' in Europe.
"These teams are coming to play us, looking at it as a cup final so they will try anything they can to beat us," he told the media, as reported by the likes of the Daily Mail.
"We have to be streetwise to that, deal with that and let our football do the talking. But that is what they are going to try to do. They are going to try everything to get an upper hand on us. James Tomkins was sent off in the last game and Sakho in the game before. That can't happen. We need to be more streetwise."
If Collins had practiced what he preached the Hammers would be all but qualified for the final play-off round with Bilic afforded the luxury of resting key players for next week's second leg ahead of the Premier League opener against Arsenal three days later. But the 31-year-old made an unnecessarily rash challenge to get his first booking and played into Astra hands by picking up another, albeit slightly harsher, booking just minutes later. In his absence West Ham conceded two costly away goals and not only face an uphill task for the second leg but a game where they must field a strong side.
3) Payet will be a star for Hammers this season
Dimitri Payet showed just why Slaven Bilic made him his number one target after taking over the Hammers with some sublime touches on his competitive debut for the club. The 28-year-old Frenchman dictated the play and set up the first goal until the sending off clipped his wings somewhat as the Irons were forced to restructure their line-up. Many fans hope he can emulate the likes of Paolo Di Canio at the Boleyn Ground such are his mercurial talents. They are big shoes to fill but he is most definitely capable on this showing and is only going to get better.
4) Valencia injury means timely Sakho return could save the day
West Ham know they must now win in Romania to progress but their list or injuries and suspensions is already a major headache for Bilic. Next Thursday he will be without James Tomkins and James Collins while Joey O'Brien and Enner Valencia both came off injured. Carl Jenkinson is not yet fit to play while Winston Reid missed the game through injury and it is not yet known if he will be available. Andy Carroll is out until at least September and Modibo Maiga has no future at the club.
Therefore the return of goal hero Diafra Sakho cannot come quick enough and the Senegal striker should be back for the away leg after missing the last three Europa League matches following his own sending off in the first round. He scored twice in his only full competitive game so far this pre-season and he could prove the difference for the Hammers in Romania.
5) Reece Oxford IS the new Rio Ferdinand
Anyone watching West Ham's youngest ever player tonight will have seen the 16-year-old blossom in front of their eyes. It was like watching Rio Ferdinand's early development all over again as he was thrust into the heart of midfield to help quicken his feet up ready for a long career, hopefully at the top for West Ham and England.
So similar in style and build to Rio, perhaps even taller and more athletic, Oxford looked assured when he moved into central defence after Collins' sending off and coped admirably with a late onslaught from the Romanian visitors. May well spend some time out on loan, particularly if the Hammers fail to make it through to the group stages, but he has a big future in the game on this showing.