By virtue of a fourth-minute headed goal from Michel Ngonge, Watford - seeking successive promotion after winning the Second Division title last season - will travel to St Andrew's for Thursday's second leg with a measure of security.
"It must give us some advantage," the former England manager acknowledged, eventually. "But we can't afford to go to Birmingham thinking in those terms, or we might get sloppy. We have to put this to one side and go there looking to win another game."
Winning this game turned out to be something of a sweat. The final whistle was greeted with relief by most of the 18,535 spectators present following the 76th-minute sending off of home defender Paul Robinson for a wild challenge on Peter Ndlovu.
Taylor's pre-match assertion that the visitors could not stop his players running and working proved to be correct. From the start, they harried for every loose ball and counterattacked with speed and purpose. Their goal stemmed indirectly from this attitude as Birmingham's full-back Martin Grainger was forced to concede a corner under pressure. Peter Kennedy floated the ball in to the near post from Watford's right, where Ngonge met it perfectly to open the scoring.
Within 10 minutes Kennedy had missed two other chances to increase Watford's margin, misdirecting a shot when he found himself unmarked in the area, and then heading wide.
A match which eventually saw seven players booked then developed into what Taylor called "a battle", and as half-time approached there were signs that Birmingham had steadied their nerves. After 22 minutes, the former Watford striker Paul Furlong headed over and soon afterwards Chris Holland forced Alec Chamberlain to save smartly with a 25-yard drive.
The second-half arrival of Dele Adebola put Watford's defence under even greater pressure and the 6ft 3in forward, still regaining full fitness after hamstring injuries, had two clear chances to equalise. After 62 minutes, with Chamberlain out of position, he chipped over; 10 minutes later he got the ball caught between his feet after the Watford keeper had mishandled a high cross, allowing Watford's defence to scramble clear. "A fit Adebola would have scored," Birmingham's manger, Trevor Francis, ruminated afterwards.
But Watford held on for their eighth win in nine games. Form appears to favour them - but you won't find Taylor saying that.
Goal: Ngonge (4) 1-0.
Watford (4-4-2): Chamberlain; Bazeley, Palmer, Page, Robinson; Wright (Smart, 67), Hyde, Johnson, Kennedy; Mooney, Ngonge (Hazan, 83). Substitute not used: Day (gk).
Birmingham City (4-4-2): Poole; Rowett, Holdsworth, Johnson, Grainger; McCarthy, Robinson (Ndlovu, 68), O'Connor, Holland; Bradbury (Adebola, h-t), Furlong. Substitute not used: Purse.
Referee: C Wilkes (Gloucester).
Bookings: Watford: Page, Robinson, Mooney; Birmingham: Furlong, Rowett, Grainger, O'Connor. Sent off: Robinson.
Man of the match: Hyde.
Attendance: 18,535.Reuse content