There were no fireworks this evening for the Hornets, and while Almen Abdi hit the crossbar in the final moments, it was from a cross rather than a shot - an incident which kind of summed up a nearly-but-not-quite game all round for Gianfranco Zola's men.
Joel Ekstrand impressed on his full debut for Watford, replacing the injured Fitz Hall, and in the round, it concludes a useful four-point few days for the Golden Boys - even if there's a sense they should have capitalized on Saturday's fine win over Leicester City.
This division has no gimmes in it in terms of results, and Millwall were definitely worth a draw on the night.
Saturday goalscorer Almen Abdi's fourth-minute turn and curling shot very narrowly wide of Millwall's goal suggested promise for the first half - but it was far from that.
Largely attritional, Millwall kept their shape particularly well and Watford found it tough to break down a side whose two wide midfielders (James Henry and Chris Taylor) worked exceptionally hard to restrict the extra flank options that 3-5-2 can create.
Lions' loan striker Chris Wood ought to have done better on 17 minutes. After Lloyd Doyley had inadvertently diverted a long free-kick into his path just eight yards out, the New Zealand cap scuffed wide, seemingly without a deflection. Ref Gavin Ward gave a corner, maybe in sympathy.
Nathaniel Chalobah was nearly punished for losing possession needlessly just after the half-hour mark. Millwall countered with purpose. and the ball fell to Darius Henderson 18 yards out on the angle. The ex-Watford Play-Off winner cut inside his marker but fired wastefully over on his weaker right foot.
A batch of pre-interval chances for Watford flattered the hosts, who had been ponderous in possession and lacking the expected sparkle and tempo.
Abdi's low shot straight at Lions' keeper David Forde on 42 minutes was followed up with Tommie Hoban popping up in the opposition's penalty box again. The centre-half turned the ball goalwards with his thigh but again Forde smothered with relative ease.
Deep into first-half injury-time the Hornets enjoyed their best chance. Daniel Pudil's cross was beaten out by Forde under pressure from Deeney, and Forestieri - following up on the rebound - lobbed goalwards but sufficiently weakly to allow a covering defender to head clear off the goal-line.
And while the second 45 started and continued at a brighter rate of knots, there wasn't a sense that a goal was imminent.
Shane Lowry was first to create danger at either end. He overlapped neatly down the left on 51 minutes but saw a low centre beaten out by the alert Manuel Almunia.
Troy Deeney's 55th-minutes shot on the turn had the Rookery up celebrating for an instant, but the ball hit the stanchion behind the goal before rippling the back of the goal netting.
On 67 minutes, Forestieri's neat one-two with Troy Deeney set him on the angle 15 yards goal but his low shot scuttled just wide of the far upright.
The next incidents of note, try as both sides might - with Watford slightly shading it, came five minutes from time.
It was Jonathan Hogg with a 20-yard drive, still searching for his first Hornets' goal, who blazed wide of Forde's goal.
The biggest near-miss came just as injury-time was being declared. Abdi wormed his way to the corner of the area and crossed hopefully. It swirled menacingly towards and over the flailing Forde before hitting the crossbar. Pudil made a great attempt at converting the rebound, with an overhead volley that bounced just wide of Forde's left-hand post.
Hornets: Almunia; Doyley, Ekstrand, Hoban; Cassetti (Anya 66), Hogg, Chalobah, Abdi, Pudil; Deeney (Geijo 83), Forestieri (Vydra 73).
Subs not used: Bond (GK), Yeates, Smith, Thompson.
Goals: none. Yellow Cards: Pudil (59), Hogg (71), Chalobah (77). Red Cards: none.
Lions: Forde; Smith, Shittu, Beevers, Lowry; Henry (Wright 52), Abdou, Trotter, Taylor (Feeney 88); Wood, Henderson (Keogh 52).
Subs not used: Taylor (GK), Smith, Osborne, Malone.
Goals: none. Yellow Cards: A Smith (27), Taylor (69). Red Cards: none.
Att: 11,293 (950 Lions fans).Ref: Gavin Ward.