Rovers Reserves were undone by two set-plays, as they slipped to their fourth defeat of the season at home to league leaders West Ham.
The visitors converted corners in each half, with Paul McCallum heading home the opener on 18 minutes, before Matthias Fanimo back-heeled the ball over the line after the break.
Rovers failed to hit the same heights as their last outing in the Barclays Under-21 Premier League, when they romped to a 4-2 win over Reading, with several half-chances falling the way of Osayamen Osawe the closest they came to threatening the scoresheet.
Gary Bowyer named a number of players with first team experience in his starting line-up, with Jake Kean getting a run-out in goal, Adam Henley and Josh Morris operating down the right and Portuguese duo Paulo Jorge and Edinho also involved. Jack O'Connell and Raheem Hanley returned for the Reserves after being away with England's Under-19s.
Rovers started the brighter of the two teams and had the game's first effort at goal on 10 minutes, but Hugo Fernandez's ambitious 30-yard volley sailed well wide.
A minute later, a quick Rovers break ended with Osawe firing a ball in from the right, which caused concern for the West Ham defence, who did well to avert the danger.
The visitors gradually grew into the game and opened the scoring with their first meaningful attack on 18 minutes. Following a foul by Morris, Robert Hall whipped in the free-kick from the left, Daniel Potts brought it down and Jordan Spence ballooned over the bar from close range. But the shot took a slight touch on its way over and from the resulting Hall corner, McCallum stooped to head home.
On 25 minutes, another Hall free-kick dropped to Sebastien Lletget just outside the box and his crisp deflected strike was well saved by Kean low to his left.
Two minutes later, Fanimo had time and space to pick his spot, but his swerving left-foot strike crashed off the outside of the post.
McCallum thought he had doubled the visitors' lead on the half-hour mark when he again headed home, this time from a cross from the right, but the striker had just strayed offside.
The final chances of the half both fell to Rovers, but Osawe blazed over after latching onto a ball over the top, before Fernandez headed wide at the far post.
Frenchman Frederic Piquionne replaced goalscorer McCallum at the break and the visitors were quickly back in their stride, Hall showing some silky skills on 48 minutes, before shooting straight at Kean from the edge of the area.
Ten minutes later, patient build-up by Rovers resulted in Henley crossing for the unmarked Osawe in the middle, but he sent his free header over the bar.
Morris saw a shot comfortably saved by Stephen Henderson on 71 minutes, but a minute later, the Hammers doubled their lead. A Hall corner from the left was headed goalwards and Fanimo's back-heel was adjudged to have just crossed the line before Rovers could clear.
Bowyer made a triple change late on, with Kellen Daly, Will Beesley and Curtis Haley all entering the fray, but they were unable to affect the outcome.
Rovers are back in action on Wednesday afternoon when they take on Oldham Athletic in the first round of the Lancashire Senior Cup at Brockhall (kick-off 1pm).
ROVERS: Kean, Henley, O'Connell, Wylie, R. Hanley, Fernandez (Haley 83), Jorge, O'Sullivan (Beesley 83), Morris, Osawe, Edinho (Daly 82).
Subs not used: Dilo, Laverty.
WEST HAM UNITED: Henderson, Driver, Potts, Moncur (Mpanzu 82), Chambers, Spence, Turgott, Lletget, McCallum (Piquionne 46), Fanimo, Hall (Lee 85).
Subs not used: Baxter, Hunt.