London: Per Mertesacker believes Arsenal`s midweek European success will provide the ideal springboard to get back on track in the Premier League against West Bromwich Albion on Saturday.
After a difficult period that once again raised questions about Arsene Wenger`s long-term future as manager, the Gunners lifted some of the gloom around the Emirates Stadium with a 2-0 victory against Borussia Dortmund in the Champions League on Wednesday.
The dominant display secured Arsenal`s place in the last 16 of Europe`s elite club competition for the 15th successive year and now Gunners defender Mertesacker hopes they can kick-start their domestic campaign when they visit the Hawthorns to face Alan Irvine`s men.
"We were very convincing against Dortmund. We have to show character and that is what makes me really happy for the next few games, because we have to sharpen up in the Premier League as well," Mertesacker said.
"Saturday is a good chance to show everyone that we are still alive. We have secured Champions League football and that gives us a life, but that has nothing to do with the Premier League.
"Dortmund are a good example of that, because they are already through but they have suffered a lot in the Bundesliga. We have to come back in the Premier League and that is the next target."
Despite Mertesacker`s confidence, Arsenal`s return to winning ways against Dortmund was quickly overshadowed by confirmation Jack Wilshere will be out for three months.
Less than 24 hours after the Champions League victory, Wilshere underwent an operation on an ankle injury suffered in last weekend`s home defeat to Manchester United.
The loss of the England midfielder will be keenly felt, with Wilshere one of the few players to have avoided criticism during the recent, disappointing run -- which saw Arsenal slip to eighth in the league after successive defeats against United and Swansea condemned them to their worst start for 30 years.
With Mikel Arteta also sidelined with a calf problem picked up against Dortmund, Wenger is running short of midfield options.
And the Gunners suffered another blow when France Under-21 striker Yaya Sanogo, introduced for his first start since August, was forced off with a hamstring problem after scoring the opening goal against the German side.
Meanwhile, West Brom manager Irvine insists Saido Berahino is in the right frame of mind to face Arsenal despite his recent brush with the law.
It came to light earlier this week that the 21-year-old, part of England`s most recent squad, was last month arrested for drink-driving.
Albion themselves only found out about the incident on Monday and are now carrying out their own investigation
The Burundi-born player was stopped after travelling at "high speed" on a motorway in the early hours of the morning on October 22.
"Firstly, it`s an ongoing investigation and it is important I don`t say anything that jeopardises that," Irvine said.
"He did not train on Tuesday due to a tight hamstring. But he trained on Thursday and trained really well.
"I was perfectly happy with the way he trained and went about things.
"He has done really well for us this season. Everyone has been giving him praise. As far as I`m concerned his head is in the right place."
It is not the first time that the player -- who is the highest-scoring Englishman in the Premier League this term with seven goals -- has found himself at the centre of controversy.
He was pictured inhaling laughing gas earlier this year and last season was punched by team-mate James Morrison during a furious dressing-room row after a draw with Cardiff.
Morrison (illness) is a doubt, while Jonas Olsson (Achilles) is out after undergoing surgery.