Gareth Bale may be forced to wait a while longer before making his first start in the Champions League for more than two years after the Real Madrid manager, Carlo Ancelotti, reminded an expectant public he had to be "careful" with the £86m world-record signing's fitness in the wake of a heavily disrupted pre-season.

The Welshman has travelled to Istanbul for Tuesday's opening Group B game against Galatasaray as part of a 20-man squad having played just over an hour of Saturday evening's 2-2 draw at Villarreal. Bale's summer preparations were affected by groin and foot injuries, as well as by the protracted nature of his move to Spain from Tottenham Hotspur, and he had only three days' training with his new team-mates before that scoring debut at El Madrigal.

Although the player would expect to begin against Gala, where Real will begin their latest quest for La Decima – a 10th European Cup – Ancelotti may opt to start with Ángel di María on the right flank and use Bale from the bench, particularly with the forward sure to feature against Getafe at the Bernabéu this weekend. "The team will be similar to that which played at Villarreal at the weekend but we will have to see how Bale trains," said Ancelotti, who is overseeing his first Champions League game in charge of the club having won his first equivalent fixture at each of the five clubs he has previously coached. "We have to be careful with him after the difficult pre-season he has just had."

Bale, whose last appearance in this competition was a quarter-final for Spurs against Real in April 2011, found himself overshadowed in the buildup to this fixture by Cristiano Ronaldo's new five-year contract at the club, a deal worth €18m (£15m) a year after tax, and the continuing intrigue surrounding the captain Iker Casillas. The Spain goalkeeper, 32, has not played a competitive game for his club since mid-January and had watched his replacement, Diego López, excel at Villarreal but Ancelotti's policy of rotating the pair in European and domestic competitions will see him return in Turkey.

"I'm doing that simply because I have two top-quality goalkeepers, both of whom have a fantastic attitude, and so in my opinion Diego deserves to play in La Liga and Iker, with his level of professionalism, his focus and his ability, deserves to be our goalkeeper in the Champions League," said Ancelotti. "He has so much experience that coming back in will not be a problem. He is calm and I'm sure will play a great game. Certainly the pressure will not get to him."

Regardless, the game has the potential to prove an awkward occasion for the visitors. Real's backline laboured against Villarreal – Álvaro Arbeloa has returned to the squad since then but is lacking match fitness – and were often exposed. Although the Spanish club prevailed against Gala in last season's quarter-final, they succumbed 3-2 in Istanbul and were subjected to quite a buffeting that night in April.

The home side's manager, Fatih Terim, has overseen only one win from four domestic league games this term but he has been quick to stress no side can expect a "comfortable" visit to Gala. The Turkish club have lost only two of 14 home European matches and their veteran forward Didier Drogba is confident his side can scare Real as they seek to force a passage from this section. Certainly, if that is to be achieved with Juventus also in the group, the Turkish club will have to thrive in their home fixtures.

"People will look at the teams in the group and think we can only finish third or fourth, but anything is possible. I believe in this side and we have a good chance to qualify [for the knockout stages]," said Drogba, who opened his account for the season in last week's draw against Antalyaspor. "This is a new season but we know we can beat Real again. Their players were in shock when they came here last season. After the game they said it was a crazy atmosphere here, so we have to reproduce that. We have enough power to beat Real Madrid, and we have to believe we can win."