"He's still learning the game, really, which I know sounds weird because he is now an England worldwide, but he has so few league appearances that he is incredibly raw".
His effervescent display was all the more remarkable considering his recent adversity at club level - he scored just four goals after the turn of the year - and the withering criticism from United manager Jose Mourinho.
"You can see that a lot of the lads are confident".
"I know I shouldn't mention it but I've got a tattoo of it on my arm!" he said this week of the No.10 after some unwanted attention for tattoos.
Rashford, who impressed throughout with his speed and control, fired England ahead in the 13th minute, unleashing a dipping drive from the right which flew past Costa Rica keeper Keylor Navas.
Jesse Lingard and Dele Alli are both more natural fits for that kind of task but Henderson has played the number eight position in the past and would have no concerns about doing so again in Russian Federation. By taking risks they show the glimpses of quality like Marcus's opening goal. The team were preparing for their warm-up match against Costa Rica later that evening in Leeds which they ended up winning 2-0, meaning that they head to Russian Federation having won both of their warm-up games.
England's players were given a final pre-World Cup break after the Costa Rica match, before reconvening on Saturday evening and lining up for an internal match on Monday.
Costa Rica face tournament favourites Brazil as well as Serbia and Switzerland in Group E, and will need to show far more ambition once they get to Russian Federation if they are to replicate their heroics of four years ago.
A storming run from midfield by Jordan Henderson directed him to the edge of the box where he took a shot at Navas, who forcibly pulled it away for a corner.
England's rhythm was then stunted by five quickfire substitutions, including a debut for Burnley's Nick Pope in goal. Ghana, who failed to qualify for the World Cup, hit back through Kasim Nuhu before Thomas Partey fired home three minutes from time. England ensured that he was rarely in Costa Rica's line of fire.
They completed their warm-up programme with a routine win at Elland Road, with Henderson returning to the starting line-up after sitting out last weekend's win over Nigeria because of his participation in Liverpool's Champions League final defeat to Real Madrid. And it would nearly certainly mean no starting place for Raheem Sterling. Portugal opens its campaign against Spain on June 15. Algeria did not qualify.