The day is coming when Gerard Houllier will be forced to chose between Michael Owen and Robbie Fowler. It could be in tonight's second leg tie at home to Olympiakos (Network 2, BBC2). Soon both strikers will be fully fit and their boss will no longer be able to hide behind their injuries, recovery time and tiredness.

Neither would take kindly to being left out when the decision of who partners Emile Heskey is made - and the chances are that it will be Owen who gets the nod.

Houllier has challenged Fowler to double his efforts to reclaim his best form and also, predictably, denied that he will sell the striker. As he prepared Liverpool for their clash with the Greek champions - with the tie balanced at 2-2 and a place in the last 16 beckoning - Houllier appealed for Fowler to be left alone to fight his way back.

"I would like everybody to give Robbie a break and leave him alone because what he needs now is quietness and to be allowed to work," he said. "He is not back to his best level yet but it takes some time and games. Maybe he cannot play every three days. But he's working hard, his attitude is spot on and he will come back to his best in the middle of the season."

With Owen back in full training after a fortnight out with a back problem sustained in the first leg in Athens, Houllier has a difficult choice to make this week. On only six occasions has he had Owen, Fowler and Heskey fit, available and in the squad together. Fives times Owen has been in the starting line-up and Fowler on the bench.

It would seem to suggest the writing is on the wall for a player who has spent two years battling back from a multitude of injuries. Houllier can delay the inevitable by starting Owen, just back from injury, on the bench.

Liverpool should be capable of beating a Greek side who have won just one away Champions League game in 15 over the past four seasons.

Meanwhile, Rangers manager Dick Advocaat is confident Ronald de Boer has the mental toughness to overcome a family bereavement and help his side reach the fourth round, but the Dutchman is once more hampered by a knee problem on the eve of the second leg of their clash with Kaiserslautern.

It has been a bad week for de Boer. It began with a photograph of him unwittingly posing with sectarian killer Michael Stone appearing on the front page of a Sunday newspaper. Then yesterday his family were recovering from the news that an aunt had committed suicide back in his native Holland.

The knee problem is really just a niggle, and striker Michael Mols has one too. Both are set to play, but may not last until the end of a game that could go to extra-time and penalties.

Tugay has been told he will replace the suspended Barry Ferguson in a midfield role rather than the sweeper's position he filled successfully on a Champions League assignment in Monaco.

Kaiserslautern must score if they are to have a chance of knocking out the Scottish champions, who take a 1-0 first-leg lead to the Fritz-Walter Stadium.

Tonight's Fixtures

(Scores from first legs in brackets)