Sadly, its no surprise to me; Leicester did the same thing with Barnsley last season. He carried them somewhat until mid-season and his departure was the start of their demise to getting relegated. His departure shouldn't have such a pronounced effect on us, but we still need a quality replacement in as soon as possible to continue the promotion push.
Barnes sometimes doesn't do enough over the whole 90 mins, but he is one of a small number of players that can create something from nothing and ultimately score match winning goals and its this quality that will impact us most and is really difficult to replace as everybody is looking for the same qualities.
If Sako had been given more time around the first team, he would be the obvious answer. However his lack of minutes and minimal impact he's made when he's played suggests this is not the solution.
Similarly, Harper could be an option in the current Matt Phillips role, allowing Phillips to play further forward. However, I don't think the coaching team will put their faith in him when there is so much at stake this season.
Hopefully our esteemed technical director has some aces up his sleeve and Jenkins gets the cheque book out. Sadly I fear neither will happen.