The 19-year-old England youth international made just one substitute appearance for Frank Lampard's team in the Premier League and moved to Brighton in search of minutes on the pitch.
Few expected the 5ft 3in right back to make a telling contribution so soon.
Lamptey impressed the management team at Albion from day one and Graham Potter hinted ahead of the Arsenal match that the young flyer could have a role to play after the restart.
He didn't feature during the 2-1 win against the Gunners but then made a huge impact on his debut at Leicester. It was far from easy however for the youngster at the King Power.
He was on the receiving end of a few robust challenges and finished with a hole in his mouth that required a number of stitches. He played on.
It was important for Lamptey to continue and the smallest defender in the division proved he has the mental and physical qualities to cope with life in the Premier League.
In training, Brighton deliberately paired him up against their 6ft 7in defender Dan Burn - the tallest left back in the division - in order to 'toughen him up.' - Seeing Burn and Lamptey together really does prove that football is for all shapes and sizes
He excelled on his debut at Leicester and was one of Albion's brighter players in an advanced right midfield role during the first half against Man United.
Potter clearly trusts his new arrival and the player, who was with Chelsea from the age of seven, was given the nod for Norwich ahead of experienced right back and former Barcelona man Martin Montoya.
In one of Brighton's most crucial matches of the season, Lamptey was once again excellent at Carrow Road. He played with skill and control and was lightning quick when attacking.
“It’s hard to sum up those emotions at the end – it’s what you play football for. It’s a great win for the boys, we dug deep," he said.
“We have been working hard in training and listened to what the gaffer had to say. It wasn’t pretty at times but we dug in and got the three points which is the most important thing.
“I think there’s always going to be chances in a game and credit to Norwich for hitting the post late on, they’re a good team and we perhaps got away with it at the end there!
“Coming into the game, we didn’t really talk about the importance of the three points. It was just another game to play our best and get three points. I’m glad we did.”
Lamptey arrived to add competition for places at the Amex for next season but on this form he's almost an automatic choice already.
His recent contributions have played a key role in helping Brighton to all but secure their top flight status. Albion's next two matches are against Liverpool and Man City and don't be surprised to see him more than hold his own against the division's finest.
Chelsea are blessed with Reece James at right back but they may well regret allowing Lamptey to leave quite so cheaply. Huge credit to the youngster for moving in search of first team football.
£3m appears good business for Albion. They have a serious talent of their hands and in Potter they have a head coach willing to give talented young players their chance - even in the most crucial of matches.
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