Being in the Champions League is a proven gateway to international football. There was one conspicuous absence at an otherwise packed Parkhead the other night, when the seat expected to be filled by Luis van Gaal was instead occupied by someone else.
It had been thought that the Netherlands manager would attend to watch two defenders in particular: Stefano Denswil of Ajax and Celtic's Virgil van Dijk. Denswil, just 20 and full of promise, had an unfortunate night during which he brought Anthony Stokes down for a penalty and then deflected Biram Kayal's shot into the net. Denswil had many good passages of play and helped restrict Celtic to few chances, but Van Dijk delivered a more polished performance at the other end.
Neither player is capped and Van Dijk is a couple of years older. Denswil has played internationally at every age group from under-15s while van Dijk first represented the Oranje at under-19s. The Celtic defender has handled the transition from the Eredivisie to the SPFL Premiership and the Champions League with very few questionable performances so far, and any excitement about potentially becoming a full international does not seem to affect his displays.
"The talk about the national team was not on my mind before the Ajax game," he said. "Not at all. I've read and heard what has been said [the speculation regarding Van Gaal] but I was not thinking about it. I was focused on my game and I just wanted to play a good game for myself, for the fans and for the club.
"But playing international football is an ambition. It is always an ambition for every player playing at this level. You want to go as high as you can and play for your national team. The Champions League is something that keeps you in the picture. It is the highest level of club competition and you want to show what you can do in these games.
"Playing for Celtic should not be underestimated as this is a good club. But if things go well and we stay in the Champions League then that can only be positive. In the beginning, people back home thought I had made a bad decision coming here, because no-one there follows the Scottish league. But I knew what I was doing. I thought about it a lot and I knew that Celtic was an unbelievably big club. You could see that again on Tuesday.
"Does the result against Ajax maybe prove those people wrong? Yeah, but that is not my motivation or what I am thinking about. I just want to play good games to help this club. We want to build a great season. As I said, before I came here, I knew Celtic was a top club. But the fans amaze me with the support we get. The European nights are obviously special, but they are also there in the league games."
Van Gaal still has room for new faces in the squad he will take to the World Cup finals in Brazil next summer and will soon name his group for a friendly double-header against Japan and Colombia on November 16 and 19.
If Van Dijk occasionally finds his thoughts straying towards his international prospects with a mixture of hope and anticipation, then he is not the only one at Celtic. Emilio Izaguirre said that he enjoyed had an "amazing" week during which Honduras qualified for the World Cup finals and then Celtic beat Ajax. Efe Ambrose, Georgios Samaras and Mikael Lustig are involved in the play-offs.
Fraser Forster is further down the line than Van Dijk, in that he can expect to be in the squad Roy Hodgson names for England's Wembley friendlies against Chile and Germany on the aforementioned dates. "The whole England thing is a bit of a bonus at the moment," said Forster. "For me, it's all about playing well for Celtic and, if I can do that, the rest will take care of itself. It was nice to make some saves against Ajax but it was important to keep our unbeaten run going ahead of Sunday's game at Firhill.
"There has been no mention about me being used [by England] in the friendlies which are coming up. There is still a lot of football to be played between now and next month and your club form has to be good before you can even think about playing for your country. If it happens then it happens and it would be terrific. But, until it does, I'm just concentrating on Celtic."
If Van Dijk and Forster maintain their form it could work to their advantage that the next Champions League matchday, which Celtic are away to Ajax, is on November 6. Anyone who delivers a performance so close to the international dates could do much to force their way into contention for the friendlies. "It gives me the chance to help Celtic get out of the group and improve my England chances, but I'm not really thinking about that right now," said Forster. "You can imagine these possibilities but you can't really control it. You can only worry about what you can control."