World Cup qualifiers: Wales must improve defensively, says John Hartson
John Hartson does not believe Wales' World Cup qualification hopes are over but says their inability to keep clean sheets is a worry.
Wales were held 1-1 by Serbia and a third consecutive draw has left them third in Group D, four points behind leaders the Republic of Ireland.
"There's enough points on the board for us still to be competitive," the ex-Wales striker said.
"We've dropped six points in our last three games which is not a good sign."
Hartson added: "We've got to start winning games and we've got some really tough away games to come.
"We play the Republic of Ireland in March and if we can go there and get three points we only go a point behind them."
Wales face the Republic of Ireland in Dublin on 24 March and travel to Serbia in June with away fixtures in Moldova and Georgia to follow in the autumn.
Coleman's side had taken the lead in their in their previous three qualifiers but had to settle for a point in the each game.
It is a pattern which concerns former Arsenal and Celtic striker Hartson, who scored 14 goals in 51 games for Wales.
Wales have let in four goals during the current campaign, the same amount they conceded during the whole Euro 2016 qualifiers.
"If we can get back to keeping clean sheets we are going to win games because we've got goals in our team," Hartson told BBC Five live.
"It's that inability to see games out and demand from yourself to keep clean sheets like we did in the last campaign.
"That's what we've built our spirit and results on and climbing up the Fifa world rankings because we kept clean sheets.
"That's what we have to get back to."
Republic of Ireland 'have belief' they can qualify
Wales' next opponents, the Republic of Ireland, moved to the top of Group D with a 1-0 win over Austria in Vienna.
Former Irish international Kevin Kilbane says Martin O'Neill's side will be full of confidence going into next year's game against Wales at the Aviva Stadium.
"Ireland are in such a good position they can drop points and don't necessarily have to win the game," Kilbane told BBC Radio Wales' Jason Mohammad programme.
"It might cause Wales to try and force the issue a little bit.
"He's [O'Neill] got a side that's stable and there's real belief that this campaign, particularly after that Austria game, that they can top the group,"