Emile Heskey has been charged with improper conduct by the Football Association after his sending-off during Birmingham City's match at home to Arsenal last Saturday.

The former Liverpool striker, hopeful of a return to the England squad in time for the World Cup, was dismissed for two bookable offences but refused to leave the pitch promptly and twice made gestures towards Mike Riley, the referee, who has reported the player.

Heskey then made his feelings known to Phil Dowd, the fourth official, before being dragged away by Steve Bruce.

He has to serve an automatic one-match ban for the dismissal and is ruled out of the FA Cup fourth-round replay at home to Reading tonight.

But Heskey could face further punishment if he is found guilty on Friday by an FA disciplinary commission.

An FA statement read: "The charge relates to Heskey's conduct after being sent off against Arsenal on February 4. It is alleged that Heskey failed to leave the field of play promptly and approached the match officials in an aggressive manner using abusive language.

"In bringing the charge the FA compliance department relied upon evidence provided by match referee Mike Riley. Heskey has until 6pm on Tuesday to respond to the charge and the case will be heard by a disciplinary commission on Friday."

Bruce, the Birmingham manager, was critical of the decision to send off Heskey for challenges on Philippe Senderos and Mathieu Flamini.

He said that Heskey's frustrations were justified but claimed that the striker did not over-react before eventually heading for the dressing-rooms.

"You could understand Emile's frustration," Bruce said.

"That's why he reacted the way he did. For the first booking he was just watching the ball and, yes, he caught Send-eros, but everyone in the ground knew that there was no intent.

"The second booking was a foul but you can't tell me that Heskey had intentionally gone to smash Flamini. I don't think he really reacted to anything. He was disappointed."

Heskey became the seventh Birmingham player to be sent off this season.

This is hardly what Bruce would want in the run-up to a crucial FA Cup tie.

The term "injury crisis" is over-used in football but, for once, it is appropriate where Birmingham are concerned.

Bruce could be without 15 players for the fourth-round replay.

Fortunately, Reading are likely to field what will effectively be a reserve team, so Birmingham will still be favourites to progress to a fifth-round tie away to Stoke City.

Matthew Upson (groin), Olivier Tebily (knee) and Muzzy Izzet (calf) all sustained injuries during the defeat to Arsenal last Saturday and are awaiting the results of scans.

Kenny Cunningham (groin), Martin Taylor (ankle), Stan Lazaridis (groin), David Dunn (calf), Neil Kilkenny (ankle) and Mehdi Nafti (knee) are already already sidelined, while Chris Sutton and Nicky Butt also picked up knocks.

But the tale of woe continues. Dudley "DJ" Campbell is cup-tied and Martin Latka, the Czech Republic Under-21 international defender, is ineligible because his move to Birmingham came after the original tie between Birmingham and Reading. Heskey and Damien Johnson are suspended.

With Bruce wondering what he has done to deserve such treatment, his assistant, Erick Black, tried to put a positive spin on the matter. It was a forlorn attempt.

Black said: "I think we've got about 14 or 15 players that might not be available to play. We are going to have to assess everything on Tuesday afternoon as we are waiting on scans and 24-hour recoveries. We might have one or two that are better by Tuesday."

If Upson plays, it will be a chance to renew acquaintances with Reading, the club for which he played on loan while he was employed by Arsenal.

Upson said: "I had a good loan spell at Reading and it was where Birmingham watched me. I really found my game there and got really fit. I got sharp and really enjoyed my time there.

"They had a really good manager in Alan Pardew who helped me while I was there and I wish them all the best in the league. I hope they get promotion. They are a good football club.

"I will be thinking differently on Tuesday, though, as I am desperate for a good Cup run. We have got a decent tie if we get through so we have to go all guns blazing.

"I turned up at Reading and, for my first two games, I was all over the place. I was poor. The manager left me out of the team in my third game, which was a bit of a blow to my confidence. It was a reality check of how unfit I was and how I needed to approach the game and it has done me the power of good. I turned things around and really finished strongly.

"All credit to them as they have a good balanced side and they have won again [at the weekend]."

Despite the 2-0 defeat at home to Arsenal last Saturday, Birmingham are in better shape than they were six weeks ago. They remain in the bottom three but there is hope at St Andrew's, whereas auguries were not good towards the end of the past calendar year.

Upson's form has remained consistently good this season, especially in recent matches, although his hopes of making the England squad for the World Cup in June depend on injuries to other players. Still, he remains happy with his form. He said: "I can only talk personally, but my confidence is as high as ever. I feel really comfortable when I am playing. I think the team has improved.

"We maybe lacked a little bit of energy against Arsenal after a really tough game the previous midweek [away to Liverpool]. If we could have kept the tempo as high as we normally do, then it could have been a different game.

"We had a couple of chances and I've hit the post and Maik Taylor has hardly had a save other than the goals. It was a bit of a tight angle and I tried to slide it between the keeper and the post."