* Spaniard Xabi Alonso makes first start for Bayern
* Lewandowski opens his account for the Munich club
* Leverkusen top after 4-2 win over Hertha Berlin (updates with Guardiola, Keller quotes)
BERLIN, Aug 30 (Reuters) - Last season's Bundesliga top scorer Robert Lewandowski scored his first competitive goal for new club Bayern Munich but the champions had to settle for a 1-1 draw at Schalke 04 on Saturday.
Despite having new signing Xabi Alonso in the Bayern team 24 hours after he joined on a two-year deal from Real Madrid, they looked far from their best as Schalke got their first point to snap a two-game losing run with a gutsy second-half performance.
"At this moment in the season it is not possible to play over 90 minutes the way we played in those first 25 minutes," keeper Manuel Neuer told reporters.
Lewandowski opened his account when he flicked in a pass from Sebastian Rode in the 10th minute as Bayern dominated.
"I think those first 20-25 minutes were outstanding," Bayern coach Pep Guardiola said. "After that we started losing possession and that turned out to be the problem."
The visitors, despite missing half a dozen players through injury, overran their opponents in the first half with World Cup winner Alonso, who had more touches than any other Bayern player, confidently dictating their game from the back.
However, Bayern took their foot off the gas in the second half, with Schalke pressing higher and earning a deserved equaliser when captain Benedikt Hoewedes bundled the ball over the line after Alonso tried to clear.
Bayern's players protested that Hoewedes had touched the ball with his hand but television replays showed Alonso kicking the ball off the line and on to the charging Hoewedes.
The draw put Bayern on four points from two games.
"I can't say I am happy after this game," said Bayern midfielder Thomas Mueller. "It was a tough game but we had no more chances after the 20th minute. I am frustrated that we did not manage to hold on to our lead."
The draw eases the pressure on Schalke coach Jens Keller, after they were knocked out of the German Cup by a third-tier side and then lost their league opener to Hanover 96 last week.
"Our commitment and our passion should be like that every week," Keller said. "We did not react to that early goal well early on but gradually fought our way back.
"In the past 21 months (since my arrival) we have repeatedly shown that we support each other and we pull ourselves out of difficult situations."
Bayer Leverkusen are top on six points after conceding an own goal and twice coming from behind to beat Hertha Berlin 4-2 and make it two wins out of two games.
It was a terrible afternoon for former European champions Hamburg SV, who were crushed 3-0 at home by newcomers Paderborn and are still looking for their first win of the season.
Another promoted side Cologne also enjoyed the afternoon by snatching a 2-0 win at VfB Stuttgart while VfL Wolfsburg and Eintracht Frankfurt shared the points in a 2-2 draw.
Borussia Dortmund edged Augsburg 3-2 on Friday. (Reporting by Karolos Grohmann, editing by Pritha Sarkar)