The Indianapolis Colts signed Philip Rivers in the days before Week 15, but only to the practice squad. He can be elevated on game days, of course, but his original designation might have implied he would work more as a backup and mentor to rookie Riley Leonard. Leonard played in the last three quarters of Week 14 and was, well...fine.
But the actual narrative might be different. Instead of watching Leonard rise or fall in Week 15 against the Seattle Seahawks, Rivers may be the one doing QB1 duty. At least, that is what some practice footage from Wednesday taken by The Athletic's James Boyd implies.