The Chilean international's 45th-minute strike against besiktas on Wednesday was enough to secure Champions League group-stage football for a 17th successive campaign.
Szczesny was impressed with Alexis' all-round display against the Turkish side and thinks the 25-year-old can fill the void left by Olivier Giroud's injury.
He works very hard as well so we're delighted for him to score his first goal
"I'm sure there's many more goals to come from him," Szczesny said. "He's been around for a few weeks now and we see how good he is in training. He's very sharp, and very strong as well.
"He works very hard as well so we're delighted for him to score his first goal - it will take a bit of pressure off.
"He's got plenty of energy and plenty of pace. He runs for 90 minutes and he'll be a very strong player for us. Not only scoring goals but working very hard in defence as well. He will be a great player for us."Copyright 2015 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source 28 Aug 2014