Watford’s inability to defend crosses into their own box proved to be their downfall once again as struggling Birmingham City beat the Hornets 2-1 at St Andrew’s.

Clayton Donaldson handed the Blues a dream start with an opening goal after just 90 seconds.

Fernando Forestieri’s goal soon after ensured an entertaining first half ended level but then a dour second period finished with Donaldson being left completely unmarked to head in the winner with five minutes remaining.

Jokanovic has kept a relatively settled side during his first month in charge but he rang the changes tonight – a decision which seems to have backfired.

There were five alterations to the team which began the 3-1 win over Millwall on Saturday. Two of them were enforced as Sebastien Bassong (calf) and Gianni Munari (groin) missed out due to injury, with Tommie Hoban and Lewis McGugan lining up instead. Lloyd Doyley, Ikechi Anya and Forestieri were selected ahead of Daniel Pudil, Keith Andrews and Matej Vydra.

This was Gary Rowett’s first home game in charge of Birmingham City so an early onslaught was to be expected. But that didn’t stop one of Watford’s new additions to the line-up, McGugan, foolishly attempting to beat an opponent on the corner of his own area and it contributed to the home side taking the lead inside 90 seconds. McGugan was dispossessed wide left and Stephen Gleeson was allowed to cross. Donaldson’s deflected shot from ten yards left Heurelho Gomes rooted to the spot to hand Rowett a dream start.

But the Hornets equalised with the game’s next attack of note, five minutes later, and McGugan went some way to making up for his previous error. The midfielder slid a ball to Doyley, who was making his 400th start for the club, and the left back’s low cross found Forestieri eight yards from goal. His initial shot was too central and saved by Darren Randolph but the Argentine-born forward sent the rebound into the bottom corner to make it 1-1.

Odion Ighalo has impressed of late and he played well once again. Good work from the forward and Troy Deeney allowed McGugan to send in a dangerous delivery which flashed across the Blues’ goalmouth and was cleared for a corner.

There was an excellent tempo to the contest and it wasn’t long before Birmingham midfielder David Cotterill saw a stunning first-time effort from 20 yards narrowly wide of the far, top corner.

Birmingham went into the contest with just one win at St Andrew’s in 13 months – although that was under former boss Lee Clarke – but the Blues were not playing like a team lacking in confidence and should have regained the lead midway through the half. Andrew Shinnie was left completely unmarked following Paul Caddis’ cross from the right but the attacking midfielder could only head into the ground and wide, with the goal gaping.

Watford were moving the ball quickly and accurately entering the Blues’ half but on a few occasions Deeney’s touch let him down, uncharacteristically.

It was end-to-end and more poor marking from Watford saw Paul Robinson have a header goalwards blocked and the former Hornet and his Birmingham team-mates appealed for a penalty.

Cotterill was lively for the home team and he brought out the best in Gomes with a well-struck free-kick from 25 yards.

The frantic pace continued and Birmingham’s goalkeeper also produced a fine stop from Deeney’s improvised, sliding shot from the corner of the area, after Forestieri had headed back across goal.

Like minutes beforehand, Cotterill made Gomes save, this time from inside the area and this time the ball was fumbled. Joel Ekstrand cleared, eventually.

Jokanovic is a head coach who likes his team to control the game but there was little sign of that in the opening 45 minutes, from either side, which resulted in an excellent spectacle.

There were 21 league positions separating the teams heading into the match but that was not evident on the balance of play. Birmingham finished the half the stronger and Gomes was forced into another stop after Gleeson’s shot from outside the area.

There was more composure and calmness in Watford’s play at the start of the second period. After some steady build-up, Ighalo had a rising shot go over the bar from the edge of the area.

The Golden Boys were dominating proceedings at the start of the second half but moments after McGugan had an effort from distance saved, Birmingham almost took the lead when Hoban had to clear yards from his goal line with Donaldson waiting at the far post.

That lifted the home crowd and the Blues players.

Watford’s ability to defend crosses into their box is one of their major pitfalls and that was evident again when Koby Arthur was left free to head back across goal following Cotterill’s delivery from the left.

Cotterill was causing Paredes problems and the Birmingham winger’s low shot saw Shinnie bundled over at the far post as he attempted to follow-up the blocked effort. The referee wasn’t required to make a difficult decision due to the offside flag being raised.

Deeney was left isolated at times but that didn’t stop him outmuscling Robinson on the halfway line before manufacturing a through ball for Anya, who was unable to get a shot away and the ball ran out of play.

The Hornets had a couple of efforts from distance but their performance for a large proportion of the second half was flat. A change was required and Jokanovic brought on Matej Vydra with 15 minutes remaining.

But it was Birmingham’s latest substitute, Demari Gray, who was next to have a shot on goal, as Hoban cleared his low volley at the far post before Gomes could save.

The first half had been hugely entertaining and engaging. The second was not.

But the home crowd cared little when more incredibly bad defending from Watford allowed Donaldson to head in Cotterill’s cross from the right whilst completely unmarked with five minutes of normal time remaining.

Anya almost equalised immediately with a low shot from the corner of the area but the Hornets’ mini fight-back was short-lived as the Blues held on for just their second home win in 13 months.

Wins for Bournemouth and Middlesbrough saw the Cherries go top and the Hornets slip to third place in the Championship.

Birmingham: Randolph; Caddis, Morrison, Robinson, Grounds; Davis, Gleeson; Cotterill, Shinnie (Thomas 79), Arthur (Gray 73); Donaldson.

Subs: Doyle, Eardley, Edgar, Reilly, Shea.

Watford: Gomes; Paredes, Hoban, Ekstrand, Doyley; McGugan, Tozser, Anya; Forestieri (Vydra 75), Ighalo (Andrews 59); Deeney.

Subs: Bond, Cathcart, Pudil, Dyer, Murray.

Referee: Mark Heywood.

Attendance: 18,309 (1,390 away).