Gareth Southgate had a heated exchange with Theo Walcott on Thursday morning, after phoning the Arsenal forward to say he had dropped him from the England squad for the matches against Germany and Lithuania.

Arsène Wenger believes Walcott has become more “complete” and “efficient” this season and the statistics support the Arsenal manager’s assessment. Walcott has scored 17 goals in 29 appearances in all competitions at club level and he is on course to overhaul his best tally for a season – the 21 he scored in 2012-13.

Southgate has taken a different view and Walcott was the notable omission from his squad for the friendly in Germany on Wednesday and the World Cup qualifier against Lithuania at Wembley on Sunday week.

Southgate accepted the timing of the phone call was unfortunate. It was Walcott’s 28th birthday but it is a fair bet he would have reacted badly on any day of the week. He has scored more goals this season than any of the players Southgate has selected.

“I’ve got to say he wasn’t chuffed to bits to get the call,” Southgate said. “And I understand that. Did he argue his case? Yes. Quite rightly, he said: ‘I’m one of the leading goalscorers in the league.’

“I don’t mind being challenged on that. I totally respect that. I don’t expect him to be happy but I’ve got to make decisions and I think it was the right thing to call him to talk that through – even if the timing wasn’t great.”

Walcott was left out of the England squad for Euro 2016 by Roy Hodgson but Southgate had always previously included him. However, the manager suggested Walcott had not done enough when he started in the qualifiers against Malta and Slovenia in October and came on as a 27th-minute substitute in the friendly against Spain in November.

“I don’t think he transferred his early-season form into the matches we had in October and November with England,” Southgate said.

“He’s a player I still like. I’ve said to him that I’m not ruling him out but, in terms of just having him as a squad player, I think it’s a better opportunity for me to look at one or two others. With our wide players – the way we’re playing at the moment we like to get the players between the lines slightly differently. Theo is more a player who runs in behind defences.”

Earlier in the day, Wenger had talked about how impressed he had been by Walcott’s response to being dropped at Euro 2016. Walcott hired a personal trainer during the off-season, so he could return in prime condition, and he told Wenger he saw himself playing on the right wing, rather than as a central striker.

For years Walcott had said he wanted to switch from the right to playing through the middle and, on the occasions he has been given the chance, he has looked dangerous. His wish to revert to being a pure winger felt like a U-turn but Walcott has enjoyed a productive season and he has been on target in some big matches – against Liverpool, Chelsea and Manchester City in the Premier League and Bayern Munich in the Champions League. One further detail stands out. He has scored his goals across 13 matches and, in 12 of them, they have been Arsenal’s first or second of the game.

Southgate has named a host of players who can operate on the flanks, including Manchester United’s Jesse Lingard and the Southampton pair Nathan Redmond and James Ward-Prowse, who have been called up for the first time.

Wenger said: “Theo has become more of a complete player, more efficient. He can influence games. He is a focused player and he was not picked for the European Championship. Always in life, you try to get to the next level when things don’t go for you – or you think you did everything right and continue to live like you did before. He had the right response. He said: ‘What do I need to do to get higher up?’ And he did it.”