His manager, Harry Redknapp, was understandably keen to arrest the construction of pedestals but Colin Lee, his Millwall counterpart, was unrestrained. "He's the best I've seen at that age," he said.
Yet impressive as Walcott was, Redknapp will be acutely aware that his side's first victory in 10 Championship games was more directly the consequence of a series of Millwall gaffes.
The Lions continually shot themselves in the foot.
First there was Jamie Vincent's dire backpass after 18 minutes that handed Walcott his second goal in two senior starts.
Seven minutes later there was Phil Ifil's needless lunge at Neil McCann, which earned him a yellow card and cost Millwall a free-kick from which an unmarked Ricardo Fuller headed Southampton's second.
Ifil, on loan from Tottenham Hotspur, then collected an unfortunate second caution in first-half injury-time.
He was late in challenging Danny Higginbotham, but the full-back jumped clear of his outstretched leg, and told the referee, Chris Foy, as much."The ref said he didn't care and told [Ifil] to get off," Lee said. "I'll be writing a letter about that."
Goals: Walcott (18) 0-1; Fuller (25) 0-2.
Millwall (4-4-2): Marshall; Ifil, Lawrence, Williams, Vincent (Robinson, 29); Dunne, Morris (Asaba, 46), Wright, Livermore; Hayles, May. Substitutes not used: Jones (gk), Hutchison, Braniff.
Southampton (4-4-2): Niemi; Cranie, Svensson, Lundekvam, Higginbotham; Belmadi, Oakley (Wise, 68), Quashie, McCann; Fuller (Jones, 59), Walcott (Kosowski, 66). Substitutes not used: Smith (gk), Delap.
Referee: C Foy (Merseyside).
Booked: Millwall Ifil, Williams; Southampton Svensson, Fuller, Quashie.
Sent off: Ifil (45).
Man of the match: Walcott.
Attendance: 10,759.Reuse content