The cautious optimism that Manchester United took into the new season after marquee summer signings has evaporated even before the end of August and once again manager Ruben Amorim finds himself under an intense spotlight.

One point from their opening two Premier League games means that since taking over from Erik ten Hag, the Portuguese coach has earned 28 points from 29 top-flight matches in charge.

A rather unfortunate 1-0 home defeat by Arsenal followed by a 1-1 draw at Fulham would not ordinarily have put United back into the crisis mode they ended the last miserable campaign.

But on a stormy night in next to the Humber Estuary on Wednesday, defeat by fourth-tier Grimsby Town on penalties in the second round of the League Cup was arguably the lowest point of Amorim's tenure.

Gone are the days when Manchester United could shrug off the League Cup as a low-key competition to rotate the squad.

With no European football for only the second season in 35 years following last season's 15th-placed finish, United realistically had the FA Cup and League Cup as viable targets.

So Amorim's decision to make eight changes to his starting line-up for the clash at Blundell Park was surprising.

That said, he still gave a first start to forward Benjamin Sesko alongside fellow new recruit Matheus Cunha who between them cost United 130 million pounds ($175.6 million) in the transfer window.

With United trailing 2-0 after a diabolical first half, Amorim also sent on 65 million-pound signing Bryan Mbeumo and captain Bruno Fernandes after the break.

Had Cunha not made a complete hash of United's fifth penalty in the shootout when a successful conversion would have won the tie, Amorim would have been spared Thursday's inquisition.

Instead, Grimsby's journeymen and youngsters held their nerve, Mbeumo missed his spot kick and the abiding image of the night was an angst-ridden Amorim alone in his dugout, suffering through the shootout.

His post-match comments were laced with intrigue.

"I think this is a little bit the limit. I think something has to change. I think the team and the players spoke really loud today," he said.

Such was United's owners enthusiasm to replace Ten Hag with Amorim last year that they gave him a "now or never" ultimatum to jump ship in November rather than at the end of the season.

After a draw in his first game, against Ipswich Town, United were 12th in the table. They ended 15th with 42 points, their lowest ever Premier league haul and worst season since 1974.

Even the consolation of winning the Europa League eluded them as they lost to Tottenham Hotspur in the final, a side who finished 17th in the Premier League.

Amorim's win percentage in all competitions for United is 35.6% and it is a shocking 24.1% in the Premier League.