Millwall striker Steve Morison has been ruled out after suffering a muscle strain against Norwich in midweek.Jens Berthel Askou is still suspended, but skipper Paul Robinson has resumed training following a hamstring injury and could return in defence. [LNB]Doncaster Rovers will be without striker James Hayter, who picked up an Achilles injury against Burnley. [LNB]James Coppinger hurt his ankle in that game and is a doubt, while keeper Neil Sullivan (shin) faces a fitness test. [LNB][LNB] MATCH PREVIEW Millwall, who are only four points away from the play-off spots, have enjoyed five consecutive home victories and The Den faithful can expect a sixth if Doncaster's away form is anything to go by. [LNB]Rovers are yet to win away this season against a team outside of the bottom five, and have conceded a total of 10 goals in their last three matches on the road. [LNB]They travel to south London having ended a four-match losing run with a home win against Burnley, which halted an alarming slide towards the danger zone. [LNB]Doncaster striker Billy Sharp will be looking to celebrate his 25th birthday by continuing his scoring run. Sharp has netted all five of the Yorkshire side's goals in their last three away league games. [LNB][LNB] MATCH FACTS Head-to-head[LNB]• Doncaster's 2-1 win against Millwall earlier in the season means a victory on Saturday would complete their first league double over the Lions since the 1982/83 season, when both clubs were in the old Third Division. [LNB] Have your say on this match Millwall[LNB]• Millwall's defeat at Norwich in midweek was the fourth league game this season they have lost after being ahead, and the third time they have conceded a goal in injury time. [LNB]• The Lions have opened the scoring in 16 of their league games. Only Swansea have scored first more often. [LNB]• Kenny Jackett's side boast the best first-half record in the division, having led at the break 12 times and been behind on only four occasions. [LNB]• They have lost all seven matches in which they have conceded more than one goal. [LNB]Doncaster[LNB]• Doncaster have picked up only one away point out of the last available 12. [LNB]• Neil Sullivan is hoping to make his 200th Rovers appearance, and Brian Stock his 150th league appearance for the club.