The French and German internationals have formed an effective partnership to help Arsenal go eight games unbeaten since they lost the north London derby in March.
They're getting the credit they deserve because they work very hard and they're very honest lads. I'm very happy for them and it's much easier to play behind them when they are in that kind of form
Szczesny has regained his first-team place since Lukasz Fabianski suffered a rib injury and he enjoyed a front-row view of Koscielny and Mertesacker against Manchester United.
"I think they've been terrific - not only defending very well but also creating goals for us at the other end like they did last week against Fulham," Szczesny told Arsenal Player.
"They're getting the credit they deserve because they work very hard and they're very honest lads. I'm very happy for them and it's much easier to play behind them when they are in that kind of form."
Arsenal's top-four destiny is out of their hands despite a creditable draw on Sunday but Szczesny believes the Gunners will finish above Chelsea or Tottenham - if not both.
"I'm confident that we will be [in the top four]," he said. "We've got three games. I believe if we get nine points, we should be in a good position to finish in the top four, hopefully in third position.
"At this point of the season, it doesn't really matter who we play because I don't think the game against Wigan will be any easier than the game against Manchester United.
"Wigan are fighting relegation, QPR will play for their pride and Newcastle on the last day of the season is not exactly an easy game as well.
"I don't think it matters who we play but we've sent a message by not losing [to Man United] which makes our unbeaten run a little bit longer. We've sent a message to the teams around us that we are up for a fight."Copyright 2017 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