However, by the time that he departed the Emirates Stadium for Barcelona in 2007, the Frenchman was one of the most feared goalscorers in world football.
Such was the transformation, it took Henry just six years to sneak up on Ian Wright's record of 185 goals for the North Londoners, so much so that when Arsenal made the trip to Sparta Prague in the group stages of the Champions League nine years ago today, Henry was one goal shy of the Englishman.
The striker would have probably broken the record sooner, only for a groin complaint to sideline him for six weeks. Consequently, he started the clash in the Czech Republic among the substitutes, with manager Arsene Wenger having hinted that he would look to give his talisman 30 minutes towards the end of the game.
Yet, an injury suffered by Jose Antonio Reyes in the 15th minute resulted in Henry entering the action early and it would take him just six minutes to make a telling impact. He controlled Kolo Toure's long pass forward and then having spun on the spot, he unleashed an effort with the outside of his right boot that flew into the bottom corner of the net.
That goal drew Henry level with Wright and then 16 minutes from time, he made sure of the outcome and became Arsenal's all-time leading goalscorer in the process.
Robert Pires split the Sparta defence with a smart cross and having held off the attention of two opposition players, Henry beat Jaromir Blazek for a second time with a low finish from inside the penalty area.
Speaking after his match-winning and record-breaking contribution, Henry told BBC Sport: "It sounds great to hear 'Thierry Henry, record goalscorer for Arsenal'. Wrighty was a great player and will always be a legend at Arsenal. To beat his record is tremendous. I wanted to do it at Highbury but if I get the chance to score I'll take it."
Meanwhile, his manager Wenger added: "He wanted to score so much that he kept on trying and his class allowed him to score the first goal. It's an exceptional record. He's beaten it in a short time and he's not even a typical goalscorer. He's an all-round player, not a guy who lurks in the box.
"It's really unexplainable that a guy who is not only interested in scoring goals should score so many. He'll not only have a place in the history of Arsenal but in the history of football. He's still just 28 and Ian Wright was 33 or 34 when he broke Cliff Bastin's record. Thierry has a lot of time in front of him and there is a lot more to come from him."
Henry went on to score 226 goals for the Gunners before he headed to Spain, then a further two goals followed when he returned for a brief loan stint in 2012.
SPARTA: Blazek; Pergl (Matusovic), Petrous, Lukas, Kadlec; Petras, Pospech, Zelenka, Kisel; Polacek, Slepicka (Dosek)
ARSENAL: Lehmann; Lauren, Toure, Cygan, Clichy; Fabregas (Owusu-Abeyie), Flamini, Silva, Pires; Van Persie (Eboue), Reyes (Henry)