The Scotland Under-21 keeper is currently on loan at Wycombe but still trains with parent club Spurs during the week.
Archer told the Scottish Sun: "Gareth practises his free-kicks a lot after training.
"They dip, bend and just move everywhere. So when I see keepers let them in on match days I do feel sorry for them.
"It's so difficult. He's very talented but also works very hard. He always stays behind and the older keepers go inside so I stay behind and face him.
"Facing that kind of quality does help though. If I save a few it does help my confidence - although most of them do end up in the back of the net!"