William netted an 80th-minute equaliser as Celtic were held to a 1-1 draw away to Astra Giurgiu in the Europa League tonight.
Ronny Deila's side fashioned the first clear chance of the game as Johansen forced Silviu Lung Jr into a smart finger-tip save after 16 minutes.
The Bhoys continued to dominate but Craig Gordon had to be alert to palm away Seidu Yahaya's thumping drive on 27 minutes.
The visitors brushed off that scare then moved ahead through Johansen, who struck a fine volley into the top corner to give Lung no chance.
They had chances to improve on their lead prior to the break, with Lung denying Wakaso Mubarak, before the Romanian then thwarted Charlie Mulgrew on the stroke of half time.
Celtic brought that momentum out for the second half and Stefan Scepovic was guilty of not adding to their advantage by firing over in a one-on-one with Lung.
Scepovic should have been punished moments later but Constantin Budescu fired a first-time volley over the crossbar from close range for the hosts.
The Romanians ultimately drew level through the Brazilian with 10 minutes remaining, as William fired a fine strike beyond the helpless Gordon from outside the box.
Leigh Griffiths thought he had won it for Celtic but his goal was chalked off for an earlier foul.
Deila's troops were given more incentive in their search for a winner when Vincent Laban was sent off late on, but there was too little time remaining to snatch a winner.
