The Uruguayan has now scored in four successive away games this season, taking his tally to eight Premier League goals in 11 appearances.
“Luis is a great player and he doing a fantastic job for us,” Johnson told Liverpool’s website.
“He’s scoring goals for fun at the moment and the longer he does that the happier we will be.”
And the England international praised Liverpool’s character to come from behind and salvage a draw against Roberto Di Matteo’s high-scoring Blues outfit.
“If we had been offered a point before the game we probably would have taken it,” he added.
“Playing away at Stamford Bridge, it was always going to be difficult. Chelsea are very strong at home and we were expecting a tough game.
“We didn’t start well, they got the goal and usually when Chelsea go in front here they win.
“A lot of teams would have rolled over and ended up getting destroyed by four or five.
“But we have a great spirit in the dressing room and a lot of heart. We always fight to the death. We did that and got our reward. They had a tough game in Europe in the week and I think that showed in the last 15 minutes as Chelsea tired a little bit.
“We were strong and in the closing stages we really drove at them. We could have got all three points in the end but overall I think we’ve got to be happy with the draw.”